The Transatlantic Jetstream tends to be strongest at ~26,000 to ~32,000 ft. While airliners try to use them to their advantage as much as possible, they usually wont because of the increased turbulence that can occur below 30,000 ft. However, they (Dassault) probably didnt care about turbulence as much on this flight as they were trying to set a record instead.

Actually the Citation X is more than capable to land and take off from EGLC it’s one of the most powerful planes out there with the best climb rates… it’s just not on the approved list for city – and they use that list as “blackmail”… the ten would be more than capable to operate there and as you’ll might know Citation CJ1, CJ2, CJ3 and Sovereign flying there, and just to prove my point how crazy that is you actually have commercial variant of planes that can use EGLC whereas their “private jet” counterpart can’t – like the Embraer E190 and Embraer Lineage 1000 fiasco… E190 is the commercial version approved because the airline paid for its approval – the private Embraer Lineage 1000 which is lighter, faster and less noisy not approved… makes total sense right…

I miss understood the question then.

I wondered that myself since this aircraft has a max altitude of 50,000. FAR FAR higher then any commercial aircraft. I think the highest i’ve been on a commercial aircraft was 40,000.

The speed of sound is higher at lower altitudes.  Since the aircraft is limited by mach number, it can fly faster at 29000 than at 40000.
Mach .88 @ 29000 is 519 knots while mach .88 @ 40000 is 504 knots.  Also, most trans-Atlantic airline traffic is flying at between 30000 and 39000 feet.  So the flight corridor at 29000 feet will be empty.  Yes, the jet-stream is usually in the 25000 to 29000 feet range as well.

For sure wind and maybe best GS performance. Not sure.

more then likely its their economical altitude. 

Mate just at the same time than learjet, they were pioneer, since ages. And as they are made in the same plant than the mirage (merignac, bordeaux, my home), these little jets benefits from super hi tech since thirty years: the supercritical wings (allowing some mach speeds in case of sudden fall or brief error, ) fly by wire hud and many more….at a huge price, mostly with 3 engines. Now i found Bombardier since the G 4 are more elegant and in the same “rank”

@Ian Powell I am Gulfstream fan but the guys and gals at Falcon are slowly winning me over. 

Falcons are the real deal. 

@Papoum he asked what NM is. I told him… I’m very aware it’s not a measurement of speed…

@AircraftMechanic I asked “Why are groundspeed and true airspeed in “nm”, and then asked what it was, and then referred to the corresponding speed unit “Knots”.  Obviously the fact that speeds are referred to in “NM” is the problem, not the meaning of “NM” itself.

NM is Distance.
Knots is Speed (NM/Hour).
It is wrong to say Knots/Hour, which would expand to NM/Hour/Hour, which would refer to acceleration, say like gravity, until a terminal velocity is reached.

i think its nautical miles per hour? admittedly, ive never heard of that