Last year I took junior Filbert's on concorde. As is the norm some kind fellow traveller took a photo of us in front of the speed displays. I just happened to glance at it the other day and noticed something.

The displays usually show mach, altitude, outside temp, and mph speed.

In our photo the details were

Mach 2.00
Altitude 55000
DTG 1210
Speed 1350 mph.

Does anyone know what DTG is and why it should appear in place of temperature ? On the video I took I only ever saw outside temperature.

Ta.