It's strange... I've always assumed that airplane coffee is the lowest of the low-bid, el-cheapo, nobody-else-would-buy-this coffee that you could find. But yet, I've always enjoyed the coffee on airplanes, and to a surprising degree. I think every time I've ever gotten coffee on an airplane, my thought after the first sip was "OMG, that is SO good".
But, that could just be because I'm usually dead-tired, caffeine deprived, and jonesing for coffee like a crack addict craving their next hit, by the time I get on the plane. shrug