Legroom Wars: Another Plane Diverted After Reclining Seat Fight

— -- For the second time this week, clashes over shrinking legroom on a commercial airplane made tempers so hot that a flight had to be diverted from its intended destination.

The two incidents were part of a cluster of flight diversions this week, with the most recent one occurring just hours after two women allegedly consumed mass quantities of duty-free liquor on a plane, prompting a fighter jet escort back to Canada.

As planes have become more packed, flight attendants say they have seen an increase in unruly passenger incidents.

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In the latest legroom dispute to escalate, a Miami-to-Paris American Airlines flight landed in Boston late Wednesday after air marshals on the plane broke their cover to restrain a man who had fought with a passenger trying to recline in front of him, a law enforcement source told ABC News. The air marshals acted after the man allegedly grabbed the arm at a flight attendant who intervened, according to a federal affidavit.

Edmond Alexandre, 61, of Paris, was taken off the plane, arrested, taken to a Boston hospital for a pre-existing medical condition, and arraigned at the hospital today on a local charge of interfering with a flight crew. He also faces a similar federal charge, according to the affidavit.

The flight continued on to Paris.

The incident came just days after a man on a United Airlines flight used a product called a Knee Defender to keep the seat in front of him from reclining. The woman in front, unable to recline, got into an argument with the man and reportedly threw a cup of water in his face. Both passengers were seated in United’s Economy Plus section, which gives fliers extra legroom for an extra fee.

The argument prompted the Newark, New Jersey-to-Denver flight to be diverted to Chicago, United Airlines confirmed, adding that the unidentified passengers were not allowed back on when the plane continued on to Denver.

What's going on with these run-ins?

"Travelers today are more stressed than they've ever been before," said Scott Mayerowitz, an Associated Press airlines reporter. "When you finally do get to your seat, there's just less room than we've had in the past."

That doesn't explain what happened Wednesday on board a Toronto-to-Cuba Sunwing Airlines flight that needed a fighter jet escort back to Canada after two women drank "a significant quantity of their duty free alcohol purchase in the lavatory and lit a cigarette, triggering the smoke detector alarm," according an airline statement.

After the alleged mayhem in the lavatory, they then began fighting each other and made a threat against the aircraft, "which was considered non-credible given their condition," said Janine Chapman, a spokeswoman for the airline.

Two fighter jets escorted the plane back to Toronto, according to the North American Aerospace Defense Command (NORAD), which serves Canada and the United States. The women were taken into custody after it landed in Toronto.

In another recent high-profile plane diversion over an unruly passenger, a SWAT team rushed onto a plane that was diverted back to Toronto after a passenger allegedly threatened the aircraft.

Wednesday evening's incident on board the Miami-to-Paris flight was rare because air marshals jumped in. The highly trained air marshals work undercover. Their job is to protect the crew and aircraft from terrorists. But when it comes to an unruly passenger rather than a terrorist, the marshals on board have to make the call.

"We are tasked with protecting the flight deck, the flight crew, the passengers and then ourselves," said Randy Parkes, an air marshal instructor.

ABC News' Ben Candea contributed to this report.