Dave Mackett, an airline pilot and president of the Airline Pilots Security Alliance, says the diversions are costing airlines millions and leaves the industry vulnerable to lawsuits.

"This cannot be the new norm," Mr. Mackett said.

Daryle Elizabeth Lademan, an associate with DFI Corporate Services, says the economic threat comes from the burden on passengers who face stricter screening rules.

"The leisure traveler won't fly as much, the business traveler will teleconference more often or seek private air-travel options like charters, corporate jets, and fractional ownership providers," she said.