How does one interpret the satellite data on flight MH370?
TL;DR.


Use the BTO not the difference in time-stamps for request &amp; acknowledge.
BTO is an offset in μs, not a round-trip time.
There's a mean bias value (-495,679 μs) that includes the signal processing delays in equipment.
The distance is ground-station to satellite to aircraft to satellite to ground-station.


Inmarsat data

As I understand it, to calculate distance you should be starting with the Burst Timing Offset (BTO) not the difference between time-stamps in the Inmarsat data. There are latencies in various stages in the electronic processing of messages, not all of these are distance related.

Time    BTO(μS)
19:41   11500
20:41   11740
21:41   12780
22:41   14540
00:10   18040


There's an example on page 54 of MH370 - Definition of Underwater Search Areas:


  
  


The aircraft AND the satellite are in motion in three dimensions

The satellite is at an altitude of around 35,811 km above the earth's surface, the satellite is moving cyclically north and south of the equator and the aircraft is flying over a roughly oblate spheroid so changes in it's distance from the satellite are not a simple function of changes in the aircraft position relative to the surface.




Not to scale. E&amp;OE. etc



References


Inmarsat 3-F1 satellite position
Inmarsat 3-F1 satellite tracking
Inmarsat raw log data for MH370
MH370 - Definition of Underwater Search Areas