Linde and Still run a fuel cell testing in Munchen Airport in the mid 90. I know there were not realy encouraging results at that time, but sure this depends on available at that time technology..

But they will be there.. no doubt. this is just a matter of time..

As to the cost per hour: frankly, this is a trick. Calculations mostly are based on assumptions and predictions. Most of those can be turned in any directions.. Take the same working environment and ask two parties to calculate. Both will get different results..