The Transportation Security Administration spent about $30 million on devices that puffed air on travelers to "sniff" them out for explosives residue. Those machines ended up in warehouses, removed from airports, abandoned as impractical.

The massive push to fix airport security in the United States after the attacks of Sept. 11, 2001, led to a gold rush in technology contracts for an industry that mushroomed almost overnight. Since it was founded in 2001, the TSA has spent about $14 billion in more than 20,900 transactions with dozens of contractors.