The runways in AH are 1 mile long. They cannot be made longer, as they are the same distance end to end of a terrain grid square. Objects (such as runways) cannot cross over a grid line, or they do not work properly and are not allowed when building a terrain. I seriously doubt they would entirely redo the terrain making system just to add one uber plane. Plus, it cannot fit inside the bomber hanger, another prerequisite. Oh let me guess, y'all want em to redo the bomber hangers then too. For one plane.... 

Thanks for answering my question Ranger!!!
Now why can't the hangars on the fields that are NOT ABLE TO BE CAPTURED (ONLY) be modified to handle the B-29? Is that too much to ask for all the customers here who want the B-29? Keep in mind my prior post about load outs, take off performance etc. I think it would be great fun to have to practice taking off with various fuel, ammo, bomb, load outs to see what a particular pilot can get his plane to do!
Furthermore, you would have to really plan out and carryout your missions with great care. IF perked with a good amount of points you would want to bring some buddies as escorts or have them wing up with you when you get close to your run. The other posts about being more of a strat bomber is spot on! I think it would also make more use of the whole strat concept here in the game if they were able to be brought down a little more efficiently by the enemy. You'd also have to defend strats a little more, adding more dimension to the game.
So if you go back and see, with a medium loadout. Takeoffs would be dicey and require skill and airmanship. Sorry but no auto takeoffs here! You'd have to go for the long haul, high altitude.
One last thought. What if you made them juicy targets too? So that the pilot who can take them down gets extra perkies too? With that addition would that make it more attractive to add the 29 to those who oppose it so staunchly?
Hey, again thanks for the answer Ranger!