This is actually a myth that was recently busted. See this paper, which presents compelling empirical evidence of the aircraft industry from that time to show that there was no such hold-up:

http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2355673

Unfortunately, this is one of those myths, like the one of Watt's patents holding up development of steam, that gets repeated so often that people accept it without question.