Originally Posted by Non-NonRev
IIRC, the Thinkpad T40/41 draw about 70-72 watts, which is at the top limit of both the Juice 70 and of the power supplies on the airplanes. I'm just guessing, but maybe the power sources on the planes on which you experienced the problem were emitting less than the required 70 watts (my laptop only draws 47 watts so I haven't had the problem).
My T41 power supply is labeled as 16V and 4.5A, which I make 72 Watts. That is up from 54 Watts for the earlier model T series (eg my old T21). But the higher end of the power consumption is only when charging the battery, so once it is fully charged, I would expect the actual power draw to be well less than 72 Watts.