Want to avoid getting bumped on United and other airlines? Some key advice

You've booked a flight to St. Louis, and you have a ticket. Until this week's viral video of a United Airlines passenger forcibly dragged off a plane, you probably thought the trip was guaranteed.

Not necessarily. But there are key things you can do to reduce the chance of getting bumped, or "denied" boarding, if your flight is oversold or the airline needs your seat.

First, get to the airport early and check in, said Jeffrey Erlbaum, president of ETA Travel in Conshohocken. "If you are one of the last to arrive at the gate, that's an easy decision for the gate person to say 'this is the person I'm going to bump' if the flight is oversold."

Second, get a seat assignment in advance. "If the flight is oversold and you don't have a seat assignment, that's another easy decision for that gate person to make when they choose who's going to be bumped," Erlbaum said.

First-class passengers with premium seats and the airlines' most frequent fliers with elite status are less likely to get bumped, said George Hobica, founder of airfarewatchdog.com, an airfare tracking website.

"I don't think there are any ironclad rules, except flying first class and having ultra-high frequent-flier status," Hobica said.  However, first class travelers are occasionally bumped from flights, if the airline switches to a smaller plane with fewer total seats, or a federal air marshal needs a seat.

Other advice: Avoid the last flight of the day, because if there have been delays, "people are going to push to that last flight" and it may be oversold, Erlbaum said.

Fly off-peak hours and days. Monday mornings and Friday afternoons are peak travel times for business travelers. "Try to fly at hours when the flights aren't going to be as full" – midday and Wednesdays are a pretty low-travel day, he said.

"Most instances where there is overbooking, it doesn't get as drastic as what happened earlier this week," Erlbaum said. "The airlines start offering more and more money, or free tickets, or perks, or miles, and somebody says, 'For $1,000 and a free hotel night or two free tickets, I'll get off the plane.' "

"One thing that United did wrong was board the plane, knowing they were going to have to pull people off," Erlbaum said. "They handled it poorly, especially for employees to take the place over passengers. I am getting a lot of comments, and I have had some loyal United fliers second-guess flying on them again."

United Express Flight 3411, operated by the regional carrier Republic Airlines, was full, but not overbooked. Four Republic Airlines flight crew members showed up late in the boarding process, saying they needed to get to Louisville, Ky., because they had a flight the next day.

United asked for volunteers to relinquish their seats. When no one volunteered, United selected four people to bump, to get off the aircraft. Three passengers left, and one did not. Airport police were summoned, and David Dao, a physician, was dragged off.

It's not true that the four selected were randomly chosen. "We take certain factors into consideration when we determine who we have to rebook and be involuntarily de-boarded," said United spokesman Charles Hobart, who declined to give specifics. "I can get into some of those factors, but I'm not going to get into specifically why one customer is chosen over another.

"We want to keep families together. We take into consideration down-line implications for removing someone from that aircraft," he said, "in terms of whether they are going to have to spend another night at the airport, or at a hotel, what their connections are going to be to get them to their destination. Unaccompanied minors, we want to keep them together.

"Fare class is taken into consideration as well," Hobart said. On a flight, there are a number of "buckets," or types of fares that passengers pay depending on when they book and how full the plane is.

United continued Wednesday to deal with fallout from the treatment of Dao, 69, who was seen on video being dragged from the plane by police, his face bloody.

The airline said it would compensate all passengers for the cost of the flight. A spokeswoman declined to say if the payment would be in cash, frequent-flier miles or other forms.

United CEO Oscar Munoz, appearing on Good Morning America on Wednesday, said that United will never again use a law enforcement officer "to remove a booked, paid, seated passenger" from a plane. "We can't do that."

Munoz said that what happened was a "system failure. We have not provided our frontline supervisors and managers and individuals with the proper tools and procedures that allow them to use their common sense."

He said: "This is on me. I have to fix that, and I think that's something we can do."