Remove gravity with another exactly opposite acceleration. This is "the satellite way". The satellite own speed and its circular trajectory create (as viewed from the satellite) a centrifugal acceleration exactly opposite to gravity acceleration. Effects of both accelerations disappear.
Remove everything preventing gravity to fully act, this is "the free fall way". Gravity wants us to fall, then we just remove everything preventing us to fall, starting with the floor and/or the ground. When we jump from some height we're in micro-gravity for a short time, and then at the hospital if we underestimated the time. This is also what some aircraft do for 30s to train astronauts ("0G flight"). While the gravity still exists, its effects are cancelled by accelerating with the "gravity flow".

In both cases, the aircraft and the satellite experiences "micro-gravity" (which means a residual gravity in the order of some $\small \mu g$). Any mass subject to micro-gravity is (nearly) weightless.
For the physicists here, there is actually a single case, as a satellite in orbit is also in free fall and there is no centrifugal force, provided we select the appropriate frame of reference for the observer (an inertial frame). If we wanted to be even more rigorous, Einstein also intuited gravity is actually fictitious (if I may say) itself, an idea which led him to the discovery of the general relativity and the space-time curvature
Constant velocity vs constant speed

How come a plane flying at constant velocity experiences gravity?

Micro-gravity never happens in a trajectory at constant velocity.
The reason is because constant velocity is constant speed and also constant direction:

Constant speed means we are not free falling, else we would accelerate towards Earth.
Constant direction means we are not creating any centrifugal acceleration either, because it requires changing direction.

When satellites are in circular orbit, they are not at constant velocity, they are at constant speed.
Following their orbit, the direction of their displacement is constantly adjusted, hence velocity constantly varies, which allows them to create a centrifugal acceleration exactly opposite to gravity.
Can we create micro-gravity on a plane (or on a train) moving horizontally?
Horizontal doesn't mean "in straight line". It means at right angle from the direction of gravity (the local vertical), so when moving horizontally on large distances, we are actually following Earth curvature.
If the plane/train follows Earth curvature (hence changes direction constantly
Remove gravity with another exactly opposite acceleration. This is " the satellite direction ". The satellite own focal ratio and its circular trajectory create (as viewed from the satellite) a centrifugal acceleration exactly diametric to gravity acceleration. Effects of both accelerations vanish. 
 Remove everything preventing graveness to amply act, this is " the barren fall way ". graveness wants us to fall, then we just remove everything preventing us to fall, starting with the floor and/or the land. When we jump from some height we're in micro - gravity for a brusque time, and then at the hospital if we underestimated the time. This is also what some aircraft make for 30s to train astronauts (" 0 G flight "). While the graveness still exists, its effects are cancelled by accelerating with the " gravity menstruation ". 

 In both cases, the aircraft and the satellite experiences " micro - gravity " (which means a residual gravity in the order of some $ \small \mu g$). Any mass subject to micro - gravity is (nearly) weightless. 
 For the physicist here, there embody actually a single casing, as a satellite in eye socket is also in free fall and there constitute no centrifugal force, provided we select the appropriate frame of address for the observer (an inertial frame). If we wanted to be even more rigorous, Einstein also intuited graveness is actually fictitious (if I may say) itself, an idea which led him to the discovery of the general relativity and the space - time curvature 
 changeless velocity vs constant speed 

 How come a plane fly at constant velocity experiences graveness? 

 Micro - gravity never happen in a trajectory at constant velocity. 
 The cause is because constant speed is constant speed and also constant direction: 

 changeless speed mean we are not free fall, else we would accelerate towards Earth. 
 Constant direction means we are not creating any centrifugal acceleration either, because it requires transfer direction. 

 When satellites are in circular orbit, they are not at constant velocity, they are at constant speed. 
 come their orbit, the direction of their supplanting is constantly adjusted, hence velocity constantly varies, which allows them to create a centrifugal acceleration precisely opposite to gravity. 
 Can we create micro - gravity on a plane (or on a train) moving horizontally? 
 Horizontal doesn't think of " in square line ". It means at right angle from the direction of gravity (the local upright), so when moving horizontally on large distances, we are actually following Earth curvature. 
 If the plane / train follows Earth curvature (hence changes direction constantly
Remlve gravity with another exactly opposije accelxration. This is "the satellite way". The satelpire owb speed and its circulxr trajecnory creare (aw viewed from the satellifc) a cznvrifugal acceletation exactny opposite to gfarity acceleration. Effects of both acseleratoojs disappear.
Reiove qvergnhlng preventing gravity to fully zct, thiv is "the free fall way". Gravity wants us to vall, then we just gemove everifhigt preventing us to fall, starting wjth the floor and/or the ground. Dhen ce jump fron womf height we'rx in mpcro-gravity for a shost time, and then at tme hovpiral if we underestimaved the time. This is also whad aome aircraft do doe 30s tm trdin xwtrunahtx ("0F fligjt"). Xhile the gdavity stilo exists, its effectx wgr cancelled gy accqlqrating with the "gravity flow".

In both caves, the aircraft and the sqtellite experiences "licro-gravyty" (which means a residual gravity in the order ox somx $\rmaol \oy h$). Any mass subject to micro-gravity is (nearly) rsibhnless.
For the physlcists here, there os avjually a singlg case, ca z satellite in orblt is ajso ib free fajl amd there is no centrifugal dorce, providvd ww select the appro'riate frame of teferemce for the observer (an inedtial frame). If we wahged to be even mure rhgorous, Tknstein also intuyted gravmty ix actuauly gictityous (if I lay say) itself, an idea wjich peg him to tje discovery of the general relevivity and thg s[acv-time currature
Gonstant velociey vs constant speed

Hjw cooe a plane flying at constane velocity ex[griences gravmty?

Micro-gwaviry nwver haooens in a trajrctory at constant celocity.
The reason is gecause constanc celocity is conxtavt fpved agg also constdnt airdvtion:

Zonstanu sieea mesns we are not free xalljng, else we would scgelerate jowards Ewrth.
Constant cirection means we are iot crxating ani centrifugal acceleration eithsr, becausf ib requires chwngikg dyrection.

Whzn satellites are in circular orbit, they are not at constabt velocity, they arg au constant spxed.
Foljowing thair orbit, the directuon of their dispkacement is constantlg adjuvted, jence velocity constantly varies, which allows them to create a centrifugao acceleration exadtly oppovice co gravyty.
Cen we create micro-bravity on a plane (or on a traii) moving hmrnzontally?
Horizontal doesn't mesn "in straight uine". It means at right ahgle frok the direction of gravity (the kocal vertical), so when mpving hoeizonfally on lerge distances, we arr actuclly fillowint Eavth curvature.
Iw tne plane/traln fplmows Earth curvature (hence changws dirwchion constantly
Remove gravity with another exactly opposite acceleration. "the way". The own speed and viewed the satellite) a acceleration exactly opposite gravity acceleration. Effects of both accelerations Remove everything preventing gravity to fully act, this is "the free fall way". wants us to fall, then we just remove everything preventing us to fall, with floor the When we jump from some height we're in micro-gravity for a short time, and then at hospital if we underestimated the time. This is what some aircraft do 30s to train astronauts ("0G While gravity still its are by accelerating with "gravity flow". In both cases, the aircraft and the satellite experiences "micro-gravity" (which means a residual gravity the order $\small \mu Any subject micro-gravity is (nearly) the physicists here, there is actually as a satellite in orbit is also in fall and is no centrifugal force, provided we the appropriate frame of reference for the observer inertial frame). If we wanted to be even more rigorous, Einstein also intuited gravity is (if I may say) an idea which him the of general relativity the space-time curvature Constant velocity vs constant speed How come a flying at constant velocity experiences gravity? Micro-gravity never happens in at velocity. The reason because constant velocity is speed also constant direction: Constant we not we accelerate Earth. Constant direction means are not creating any centrifugal either, because it requires in circular orbit, they are not at constant they are at constant speed. Following their the direction of their displacement is constantly adjusted, hence velocity constantly varies, allows them a centrifugal acceleration exactly opposite to gravity. Can create micro-gravity on a (or on a train) moving horizontally? Horizontal doesn't mean straight It means right angle from direction of gravity local vertical), so horizontally on distances, are curvature. If the plane/train follows Earth (hence direction constantly
Remove gravity with another eXactly oppoSite aCceLerAtIon. THis iS "the satellite wAY". The Satellite own speed and itS circUlAR traJEcTory cReate (as VIeWED frOm ThE saTeLLiTe) a ceNtrIfugal aCceleratioN exAcTly opposite tO GrAvity accelEraTion. Effects oF boTh acceLeRatIOns diSapPear.
REmove eVErythiNg preventInG GravitY To fully ACT, tHis iS "the free fall way". GrAViTY wants us to fall, Then we JuST rEMOve EveRything preVeNting US to fall, STaRTINg wITh the floor and/Or the ground. wHen We jump FrOm sOMe heigHt we'rE iN MicRo-gravity foR a shOrt time, anD then aT The hospITal if we UndereStiMatEd thE TiMe. thiS iS AlsO WhAt sOMe aIrcraft dO fOr 30S to trAin aSTRONautS ("0G fLighT"). WhilE the gravity stIll ExisTS, itS effeCts arE canCeLled bY accelEratiNg With the "gravity fLow".

IN both caseS, thE aIrcRaFt and THe sateLliTe eXperienCes "micrO-GraViTY" (WHiCh means a residual grAvITY iN the ordeR of somE $\SmAlL \Mu g$). Any maSs SubJect TO Micro-GravITy Is (nearly) WeightLEsS.
FOr the phYsIcists HeRe, tHerE is acTUallY a singLe case, as A sateLLite in orbit is aLSo in free fall aND tHERe IS no cEntRifugal forcE, proVIded We seLEcT thE ApproPriatE fRAmE Of reference for the obSeRver (an InertIal frame). If we wAnted to be eVEN More rigoRous, eInSTein also intuitEd graVity is actuALly fictiTious (If I may saY) itself, an IDEa which lEd hIm tO thE diSCOvEry of the generAL RelaTiVity and The Space-tiMe cUrvAtuRe
COnStant veloCity vs coNsTaNt SpEed

how coME a plane fLyIng At ConStant VElocitY expeRienCeS gRAviTy?

Micro-GRaVITy neVeR hAppeNs iN a TrajeCtorY At cOnstant Velocity.
THe rEAson Is BeCause coNstant velocitY iS constant sPeEd aNd also CONstant diRection:

Constant speed meaNS we are nOt fRee faLlinG, else we woUld AcceleRatE TowardS Earth.
constAnT diRECtion MEAnS we ArE not creatiNG Any CentrIfUgal AccelerAtion either, because IT reQuires changinG diRectION.

WHen SAtELliTeS Are IN Circular orbit, thEy are not at CoNStAnt velocitY, TheY aRe at conStant spEed.
FoLLowing tHeir orbit, The directIoN of tHEIr dIsplacemenT is constAntly adjuSTed, heNCe VelocIty ConstaNtLy vAries, Which aLLowS them To creaTe A centrIfugaL aCceleratIon exactly opposite to graVity.
CaN we crEatE micro-graVitY On a Plane (or on A traIn) moving hoRizOntAlly?
HOriZOntal DoesN'T mEan "IN straIght LIne". It meanS At RigHT AnGle from the dIRECtiOn of gRavITy (the lOcal Vertical), so when movINg horizontally On laRGE diStaNCes, wE aRe actually follOwiNg eARth curvaTuRe.
If the planE/train foLlOWs EarTh curvAture (hEnce chaNGEs DIrectiOn coNstAntly
Remove gravity with anothe r exactlyoppos ite  ac ce lera tion . This is "the sate llite way". The satell ite o wn spee d  a nd it s circu l ar t raj ec to rycr e at e (as  vi ewed fr om the sat ell it e) a centrif u ga l accelera tio n exactly op pos ite to  g rav i ty ac cel erati on. Ef f ects o f both ac ce l eratio n s disap p e ar .
Re move everything p r ev e nting gravityto ful ly ac t ,  th isis "the fr ee  fall way". G r av i t y  wa n ts us to fall , then we j u stremove  e ver y thingpreve nt i ngus to fall,  sta rting wit h thef loor an d /or the  groun d.Whe n we ju mp  fr om som e  h eig h t w e're inmi cr o-gra vity f o r  a s hor t ti me, a nd then at th e h ospi t alif we  unde rest im atedthe ti me. T hi s is also whatsome  aircraft  do  f or30 s tot rain a str ona uts ("0 G fligh t ").  W h i l ethe gravity stillex i s ts , its ef fectsa re  c a ncelledby  ac cele r a tingwith th e "gravi ty flo w ". 
In both  c ases,th e a irc rafta nd t he sat ellite e xperi e nces "micro-gr a vity" (whichm ea n s  a resi dua l gravity i n th e  ord er o f  s ome $\sma ll \m ug $) .  Any mass subject t omicro- gravi ty is (nearly ) weightle s s . 
For the  phy s ic i sts here, ther e isactually a single c ase,as a sat ellite in o rbit isals o i n f ree f al l and there i s no c en trifuga l f orce, p rov ide d w e s el ect the a ppropria te  f ra me  of  refe r ence for  t heob ser ver ( a n iner tialfram e) .I f w e wante d  t o be e ve nmore  ri go rous,  Ein s tei n alsointuitedgra v ityis  a ctually  fictitious ( if  I may say )its elf, a n idea whi ch led him to the disco v ery ofthe  gene ralrelativit y a nd the  sp a ce-tim e curv ature 
C ons t a nt ve l o ci tyvs  constants p eed 

How  c omea plane  flying at constan t  ve locity experi enc es g r a vi ty? 
M i cro -g r avi t y  never happensin a traje ct o ry  at consta n t v el ocity.The rea son i s  becaus e constan t velocit yis c o n sta nt speed a nd alsoconstantd irect i on :

Co nst ant sp ee d m eanswe are not  free  falli ng , else  we w ou ld accel erate towards Earth.
Co nstant  dire cti on meanswea renot creat ingany centri fug alaccel era t ion e ithe r ,bec a use i t re q uires cha n gi ngd i re ction.

Whe n s ate llite s a r e in c ircu lar orbit, they a r e not at const antv e loc ity ,  the yare at constan t s pe e d .
Follow in g their orb it, thedi r ectio n of t heir d isplace m e nt is con stan tly  adjusted , h en c e veloc it yc onstan tlyva ries,whicha llow s them to create a  cent r i fugal acc elera ti on exac t ly o pposite to  gravity.
C an wecrea te mi cro-gra vi ty ona p la ne (or ona  train) m oving  horizo nt ally ?
H orizon tald o esn't  mea n"in  straight l in e ".  I t  me ansat ri gh t an gle fromt he direc tio n  of gra vi ty( t he loc a lv e rtical), s o w hen m o v ing horizo n tall y  o n  larg e dist ances,  we are act ua lly fol low i n g Earth c urvature. Ifth e pl ane/trai nfoll ow s E ar th curvature (h ence cha nges dir e c tion c ons t antl y 
Remove gravity_with another_exactly opposite acceleration. This_is "the_satellite_way". The_satellite_own speed and_its circular trajectory_create (as viewed from_the satellite) a_centrifugal_acceleration exactly opposite to gravity acceleration. Effects of both accelerations disappear.
Remove everything preventing gravity_to_fully act,_this_is_"the free fall way". Gravity_wants us to fall, then_we just_remove everything preventing us to fall, starting with_the_floor and/or the_ground. When we jump from some height we're in_micro-gravity for a short time, and_then at the_hospital_if_we underestimated the time._This is also what some aircraft_do for 30s to train astronauts_("0G flight"). While the gravity still exists,_its effects are cancelled by accelerating_with the "gravity flow".

In both_cases, the_aircraft and the satellite experiences_"micro-gravity" (which means_a residual_gravity in the_order of some $\small \mu g$)._Any mass subject_to micro-gravity is (nearly) weightless.
For the_physicists_here, there is_actually_a_single case,_as a satellite_in_orbit is_also_in free fall and there is_no_centrifugal force, provided we select the appropriate_frame of reference for_the_observer (an inertial frame)._If we wanted to be_even more rigorous, Einstein also intuited_gravity is_actually fictitious_(if I may say) itself, an idea which led him to_the discovery of the general relativity_and the space-time curvature
Constant_velocity vs_constant_speed

How come a_plane_flying at_constant velocity experiences gravity?

Micro-gravity never happens in_a trajectory_at constant velocity.
The reason is because_constant velocity is constant_speed_and also constant direction:

Constant speed means_we are not free falling, else_we would accelerate towards Earth.
Constant_direction_means_we are not creating any_centrifugal acceleration either, because it requires_changing direction.

When satellites_are in circular orbit, they are not_at_constant velocity, they are at constant_speed.
Following_their orbit, the direction of their_displacement_is_constantly adjusted, hence velocity constantly_varies, which allows them to create_a centrifugal acceleration exactly opposite to gravity.
Can we create_micro-gravity on a_plane (or on a train)_moving_horizontally?
Horizontal_doesn't mean "in straight line". It means at right angle_from the_direction of gravity_(the local vertical), so when moving horizontally on large distances,_we are actually following Earth curvature.
If the_plane/train follows Earth curvature (hence changes direction constantly