Richstang:
I looked through all the 1966-67 season episode info about "The F.B.I." on IMDbPro for any mention of Los Angeles Airport (and anything else possibly Shelby related that I could think of) in the synopsis, and found these two that sound promising.
Season 2, Episode 24: Flight Plan
Original airdate: Mar 5, 1967
A painting worth $500,000 is stolen from a Washington museum. A former U.S. government official is seriously injured trying to stop the theft. The thief flies to Los Angeles, intending to sell it to a collector the thief has done business with before. The thief, though, gets more than he bargained for when he meets a woman who falls for him. Erskine and Rhodes don't have much to work with. The FBI men begin to put pressure on the collector. Meanwhile, the thief concludes he'll need to kill the woman to ensure her silence.
Season 3, Episode 2: Counter-Stroke
Original airdate: Sep 24, 1967
An Eastern Bloc courier is shot and captured at an airport while entering the U.S. The courier had hidden tape intended for a mysterious operative known only as "Alexander." Erskine goes undercover, taking the place of the courier. He quickly discovers the situation is more complicated than he imagined. The FBI inspector is now in the middle of an espionage ring with conflicting allegiances. Alexander is loyal to Moscow, while other members now are loyal to China. On top of that, the courier Erskine is portraying was hired to kill Alexander. Colby and other FBI men can only keep track of the FBI inspector from a distance.