Couldn't you just set the seats in a kind of locked state as soon as the transaction arrives ( 0 confirmations) and transfer the seats as soon as it's confirmed?
This is a good idea. But the locked state needs some time limit. Maybe 24 hours?
The answer is that block 152218 followed block 152217 after a delay of 1 hour 39 minutes 7 seconds. This was the longest inter-block interval in 2011.
How about: 6 x 1 h 39 min ~= 12 hours?