Last call for alcohol could be coming soon in an effort to restore the friendly skies.

Citing her experiences as a passenger, Sen. Diane Feinstein has sent a letter to airlines asking them to impose a two-drink maximum per passenger on all flights in order to curb mounting "air rage," an effort critics say will needlessly punish responsible drinkers.

The California Democrat did not define the term air rage in her letter, but it is generally used to describe verbal or physical outbursts and abuse by passengers against other passengers or airline personnel.  

And, if the airlines won't voluntarily comply, Feinstein threatened to propose legislation that would force them to cut passengers off.

"I hope introducing this legislation will not be necessary and you will be willing to voluntarily set limits on how many drinks a passenger can consume," Feinstein said in the letter sent July 12 to officials at Continental, United, Delta, U.S. Airways, Southwest, American, and Northwest Airlines.

"I know alcohol is not the only reason for air rage, but I believe limiting its consumption is the first step your company can take to demonstrate your commitment to help ensure our skies are safe for both passengers and crew," she wrote.

The senator had not witnessed any acts of violence herself, but has seen rowdy and rude passengers in-flight, her office said.

But critics say the senator is invoking the sins of a few to punish those who feel more relaxed and in control on a flight after a cocktail.

"First of all, I would say instances of disruptive, illegal behavior are very rare and we don't believe it is reasonable or appropriate to penalize the millions of cooperative passengers for the unlawful behavior of a few," said Mike Wascom of the Air Transport Association, an airline industry trade group.

"You're going to have people who aren't nice in any circumstance. That's society in general," he said, adding that there are an estimated 665 million people traveling on domestic flights a year.

Statistics on air rage incidents vary, and it is unclear what role alcohol plays in reported incidents.

The ATA says there are about 4,000 reports of air rage a year, a number that Feinstein invoked in her letter. But the ATA says that number consists of mostly non-violent, plainly rude behavior, not blatant drunken abuse. In fact, there "is no evidence" that alcohol contributed to a majority of reports, Wascom said.

Wascom said the ATA worked with flight attendants' unions last year to get stricter Federal Aviation Administration policies put into place – such as serving no drinks before takeoff and not allowing inebriated passengers to board in the first place.

But Feinstein defended her move Monday, saying any incident is disturbing and can invariably place passengers and crew at risk.

Several well-publicized incidents of abuse on flights have drawn attention to air rage in recent years. Last April, the guitarist for the pop group R.E.M. smashed the face of a flight attendant with a vodka bottle. In the same month, two drunken sisters spit, hit and choked several crewmembers and are facing time in jail in Alaska.

But some on Capitol Hill questioned the role Congress had to play in combating air rage incidents.

"Passengers should be responsible for their own behavior, beyond that this is something the airlines should can handle on their own. Congress really doesn't have a role," said a spokesman for Sen. Conrad Burns, R-Mont., who sits on the Aviation subcommittee of the Commerce, Science and Transportation Committee.

The FAA now has the authority to impose a $25,000 fine on anyone who engages in disruptive behavior aboard a domestic air flight.