I was onboard the testflight just 2 weeks ago flying for about 3,5h hours from CPH airport up to the artic circle and back. The speed is really something, I hit about 350 Mbit/sec downspeed already on the ground at the gate when boarding the plane.
While up in the air and all passengers (including 2 E-sport players playing Counterstrike) used it the downspeed was around 150 - 280Mbit/sec downspeed and upspeed was 20-40Mbit/sec.