( CNN ) -- Two planes collided in midair Saturday in Boulder , Colorado , killing three people , authorities said . One of the planes , a single-seat Piper Pawnee , was towing a glider . The pilot of the Piper died in the collision , said Rick Brough of the Boulder County Sheriff 's Office . But the pilot of the glider , which was carrying two passengers , detached from the plane and landed safely , Brough said . Two people on the second plane , a Cirrus SR 20 , also died , Brough said . Authorities began receiving reports of a plane crash around 1:30 p.m. MT , Brough said , adding that people had seen flames in the air in an area less than five miles from the Boulder Municipal Airport . The collision was described as `` immediate disintegration and explosion of both planes , '' said Jennifer Rodi , an air safety investigator with the National Transportation Safety Board . Rodi called the glider 's occupants `` very lucky '' during a news conference Sunday and praised the glider 's pilot . `` The glider was attached to the Piper Pawnee when the pilot observed the Cirrus aircraft out of the corner of his eye , '' she said . `` He immediately noted they were on a collision course and elected to separate the tow strap from the Piper Pawnee . '' `` He did his job that he signed up for as a commercial pilot , '' Rodi said . Rodi said the Cirrus was traveling south and the Pawnee was traveling west at the time of the collision . The debris field was spread out over a couple of miles , Brough said . `` I was in my house and I heard a loud bang , '' iReporter Zac Mitchell , of Boulder , told CNN . `` I looked out my window and saw a giant fireball in the sky . '' When he went outside , he said he saw smoke and two objects , including a parachute , falling from the sky . Cirrus aircraft come equipped with an airframe parachute system that deploys in the event of an in-air emergency . It 's designed to safely lower the plane to the ground . The NTSB and the Federal Aviation Administration are involved in investigating the incident , Brough said . CNN 's Leslie Tripp , John Branch and Nick Valencia contributed to this report .
Three people were killed Saturday in a midair collision over Boulder , Colorado . One of the planes was towing a glider , Boulder County Sheriff 's Department says . The pilot and passenger died when their plane collided with another aircraft at about 10,000 feet above sea level.