The maneuver involving American Flight 2246 from Boston happened about 8:20 a.m. Tuesday, less than two hours before Southwest Flight 2504 from Omaha, Nebraska, attempting to land at Chicago’s Midway Airport, was forced to climb back into the sky to avoid another aircraft crossing the runway.

Southwest and American airlines both issued statements saying that their flights landed safely after their crews made precautionary go-around maneuvers. The Southwest pilots had to act quickly themselves to avoid the other plane while the incident at Reagan was more routine with pilots following the tower’s instructions.

Aviation experts said these kinds of moves are not entirely uncommon on commercial flights for various reasons, from bad weather to a deer walking on the runway. Pilots can execute a go-around maneuver without much notice from passengers if the plane is still flying high enough on its approach.

“It probably happens more than you and I realize,” said Robert Joslin, a professor of practice at Embry-Riddle Aeronautical University’s College of Aviation in Daytona Beach, Florida. “It’s not always just because (the plane) is getting ready to hit somebody.”

Joslin pointed to recent data from the Federal Aviation Administration. Nearly 4 out of every 1,000 arrivals at the nation’s 30 busiest airports involved go-arounds in fiscal year 2023, according to a recent FAA report. For context, the FAA handles about 45,000 flights a day.

The National Transportation Safety Board published two reports Wednesday about close calls that happened last year when planes came close to colliding at airports in Honolulu and Sarasota, Florida.

In Hawaii, several factors contributed, including the poor outdated design of the airport with several crossing runways, according to the reports. That design, combined with one pilot’s mistake of continuing past where he was supposed to stop, allowed the two planes to come within 1,173 feet (358 meters) of each other, but the controller was able to direct the Cessna to turn off on a taxiway before it reached the giant Boeing 777 crossing the runway.

In the Sarasota incident last February, one plane had to abort its landing and go around because another plane that was taking off from the same runway hadn’t left the ground yet. The NTSB blamed the controller’s error in that case for assuming the first plane would clear the runway in time and failing to properly monitor the situation.

But just like on Tuesday, a go-around the pilots initiated prevented those planes from getting within a half mile of each other.

Pilots are trained to conduct go-around maneuvers, Joslin said. And when they are relying on instruments to fly an approach to a runway in weather with low clouds, they are required to plan for the possibility of a missed approach.

There are many reasons why pilots could abort a landing, including flying too high and too fast or not being lined up with the runway, Joslin said. Another aircraft could be taxiing on the runway when it’s not supposed to or air traffic controllers could have mistakenly cleared a plane to cross a runway.

“Is it a pilot issue? An air traffic control issue? A weather issue? A wildlife issue? You name it. There are a wide variety of reasons for it,” said Joslin, who previously served as the FAA’s chief scientific and technical adviser for flight deck technology.

In the past month, there have been four major aviation disasters in North America. They include the Feb. 6 crash of a commuter plane in Alaska that killed all 10 people on board and the Jan. 26 midair collision between an Army helicopter and an American Airlines flight at National Airport that killed all 67 aboard the two aircraft.

A medical transport jet with a child patient, her mother and four others aboard crashed Jan. 31 into a Philadelphia neighborhood. That crash killed seven people, including all those aboard, and injured 19 others.

Twenty-one people were injured Feb. 17 when a Delta flight flipped and landed on its roof at Toronto’s Pearson Airport.