The percentage of seats filled on passenger planes – known as the load factor – continues to climb, making the likelihood of sitting next to an empty seat almost nil.

But airlines say they are packing us in out of necessity, not greed.

In May, the nation’s airlines recorded an average load factor of 85 percent, the highest rate ever for that month, according to the U.S. Bureau of Transportation Statistics.

The load factor for domestic flights was even higher, 86.3 percent for the month, while the rate for international flights was 82.3 percent, the federal agency said.

The nation’s airlines have pulled out of an economic slump amid an improving economy and growing demand for air travel.

But airline officials say the higher load factors are necessary to keep airlines in the black.

“On average, planes are fuller but more seats must be filled to break even because airline costs have outpaced fares,” said Victoria Day, a spokeswoman for Airlines for America, a trade group for the nation’s airlines.

In the 1990s, an airline could break even on a flight with 64 percent to 68 percent of the seats filled, according to the trade group.

By 2000, a plane needed a load factor of 69 percent to break even, with the break-even point climbing to 77 percent by 2013, the group said.

“The primary reason for the increase in cost is due to fuel expenses but other costs have risen as well,” Day said.

Anti-missile systems for jetliners?

In the wake of the downing of a Malaysia Airlines flight over Ukraine, Americans have grown fearful that terrorists may shoot down a commercial plane with a ground-to-air missile.

A new survey found that 47 percent of Americans who were questioned said they are “somewhat” or “very” worried that terrorists might shoot down a passenger plane in the U.S.

The same survey of 1,000 people, commissioned by the Reason Foundation, a Los Angeles libertarian think tank, found that 42 percent of Americans said they would be willing to pay higher airline prices to add anti-missile technology on commercial planes.

Aviation experts say the chances of terrorists shooting down a commercial plane in the U.S. from the ground are slim and the cost of installing anti-missile systems on passenger planes is prohibitive.