(CNN) -- Provocative flight attendants' uniforms used to raise eyebrows in the 1970s "Fly Me" era of aviation, but these days it's the passengers who are under scrutiny for their attire.
Saggy pants, exposed underwear and flashes of skin are getting some fliers in trouble and prompting questions about what's acceptable to wear when you're stuck in a metal tube with hundreds of strangers.
Consider these recent examples.
On September 1, Green Day lead singer Billie Joe Armstrong tweeted, "Just got kicked off a Southwest flight because my pants sagged too low!"
A local television producer who was on the same flight from Oakland, California, to Burbank, California, said a flight attendant approached Armstrong as he was trying to find his seat and asked him to pull his pants up. When he dismissed the request, she repeated it, the witness said. Armstrong was then removed from the flight.
Southwest Airlines said it was sorry about the incident.
"As soon as we became aware of what had happened, we reached out to apologize for this customer's experience," said spokesman Chris Mainz in a statement.
"He elected to take the next flight. We followed up with this customer and involved employees to get more details and, in our latest conversations, understand from the customer the situation was resolved to his satisfaction."
A tale of two incidents
In June, Deshon Marman -- a football player at the University of New Mexico -- was arrested on board a US Airways flight at San Francisco International Airport following an incident that started at the gate, when agents asked Marman to pull up his pants to cover his underwear, police said.
After repeated refusals from Marman, the crew alerted the captain to the disruption and police were called in to assist, authorities said.
The San Mateo County District Attorney's Office declined to file charges against Marman in the case.
US Airways did not reply to requests for an interview for this story, but spokeswoman Valerie Wunder said at the time that although the carrier does not have a specific dress code, it asks "passengers to dress in an appropriate manner to ensure the safety and comfort of all our passengers."
But the airline came under fire when it was revealed that just days earlier, it allowed a man dressed only in blue women's underwear, black thigh-high stockings and a blue tank top covered by a see-through cardigan to fly from Florida to Arizona.
The 65-year-old business consultant travels in provocative women's clothing for fun, but always covers up when asked by airline employees, he told the San Francisco Chronicle.
US Airways defended its actions in both cases.
Wunder said at the time that the incident involving Marman may have begun with his attire but escalated when "he repeatedly ignored crew member instructions."
When asked about the cross-dresser, another US Airways spokeswoman told CNN affiliate WSVN that crew members are "authorized to exercise their discretion."
'Offense to other passengers'
Such incidents always attract a lot of attention, but they are relatively rare.
The vast majority of passengers show up properly dressed, said flight attendant Heather Poole, who has worked for a major U.S. airline for 16 years.
"I have never seen anyone board a flight that made me think they shouldn't be allowed to travel based upon their wardrobe. Behavior, on the other hand, is another story," Poole said.
"I don't care if people want to wear flip-flops with pajama bottoms, as long as they're nice."
Still, airlines have policies in place to take action if necessary.
American Airlines has a broad mention of dress as a part of its conditions of carriage "because it is virtually impossible to write down or precisely delineate every situation that may, or may not, create an issue," said spokesman Tim Smith.
American's policy states that it can refuse to transport you, or may remove you from your flight for reasons including "being clothed in a manner that would cause discomfort or offense to other passengers."
"The crew members have the discretion to try and solve a situation as they see fit," Smith said. "If it cannot be worked out, the passenger will be denied boarding."
Incidents where passengers are actually asked to leave a flight because of the way they are dressed are extremely rare, he added.
Delta did not respond to requests for an interview for this story, but the carrier's contract of carriage states it can remove fliers whose conduct "creates an unreasonable risk of offense or annoyance to other passengers."
JetBlue warns that it can remove passengers "whose clothing is lewd, obscene, or patently offensive."
Don't fly barefoot
Southwest does not have a formal dress code in place for passengers, said spokeswoman Katie McDonald, but she declined to answer any questions about how the carrier handles travelers who might show up in questionable attire for their flight.
In addition to the Billie Joe Armstrong case this month, Southwest made headlines in 2007 for what some dubbed the "too hot to fly" incident, in which a 23-year-old woman wearing a mini skirt, a tank top, and a sweater was asked her to make her clothing less revealing. She covered herself in a blanket and was allowed to fly.
United Airlines also does not have a dress code, said spokesman Charlie Hobart. It's not an issue that's considered to be a problem, but any incident would be handled on a case-by-case basis, he said. The cabin crew does have the authority to ask a passenger to leave if he or she is deemed to be inappropriately dressed, Hobart added.
US Airways' contract of carriage states that it can remove passengers from a flight if they are "inappropriately clothed."
One thing is for sure: Don't bother showing up for your flight without shoes, unless you're a very young child.
Most airlines, including American, Delta, JetBlue, Southwest, United and US Airways, may refuse to transport you if you are barefoot.
Poole said she once saw a woman who tried to board a flight barefoot and was kicked off. The passenger was rebooked on a later flight, "that is if she could find her shoes," Poole said.