The issue is affecting all flights from the airlines regardless of their destinations.
The Federal Aviation Administration said in a statement it will investigate the emergency landing.
American Airlines showcases confidence in industry recovery by ordering 260 new jets, including Boeing's 737 Max 10 and Airbus A321neo planes.
Boeing came under renewed pressure Tuesday as the head of Alaska Airlines said inspections carried out after a dangerous incident had found many loose bolts on its 737 MAX 9 aircraft.
United Airlines said Monday it has discovered loose bolts on Boeing 737 MAX 9 planes in its fleet during preliminary inspections following an Alaska Airlines mid-flight incident.
United Airlines announced Tuesday it had ordered a total of 110 new planes from Boeing and Airbus, and secured options to purchase 90 more, in a major deal signaling confidence in the aviation sector.
United Airlines reported on Wednesday that second-quarter profits more than tripled, benefitting from robust travel demand and a surge in international capacity.
San Francisco Police said a 47-year-old man was arrested following an alleged "physical altercation" on a plane.
The other passengers had no idea that the plane reversed its course, an eyewitness said.
Jessie James Decker called out United for allegedly making her pregnant sister "clean up every drop" of the popcorn her child accidentally spilled.
The accused was charged with interference with flight crew members and attendants and using a dangerous weapon.
Delta Airlines pilots agreed to a new contract on Wednesday, agreeing to a 34% wage increase by 2026.
"There were a number of screams that were let out because it was, you know, an unusual climb at that point," said a passenger on the plane.
"[I] turned around and a gentleman, his bag was smoking," a passenger said. "He threw something on the ground ... it burst into fire."
United is giving pilots a 5% raise months early. The raise will be in the December pay period and comes after United pilots rejected a new contract proposal.
The man reportedly told a frustrated passenger that the crew was at fault and had to be blamed for the situation.
Some of the nation's largest airlines are facing choppy air as contract negotiations with pilot unions are rejected.
United Airlines shares were up more than 10% for the week, while American Airlines and Delta Airlines shares were up 7%.
United Airlines will be expanding its trans-Atlantic schedule beginning next summer.
The man admitted to taking psilocybin mushrooms before boarding the flight.
The man who was not seated near the exit door of the aircraft reportedly crawled over people to get to the door on the other side.
United Airlines is working to get ahead of what it expects to be a strong demand for transatlantic flights to Europe this summer with a historic expansion of its transatlantic flights offerings.