The Federal Aviation Administration is investigating a near-miss between two jets near Houston's George Bush Intercontinental Airport this month.
The two planes were within about a mile of each other on May 9, the FAA said.
"The closest proximity between the two planes was 0.87 miles laterally and 400 feet vertically, about two miles southeast of the airport," the FAA said.
The incident involved United Airlines Flights 601 and 437. Both had recently taken off.
"The controller issued instructions to both pilots to safely separate the aircraft," an FAA statement said.
Audio from the control tower confirms that controllers asked Flight 437 to turn right immediately, while they told Flight 601 to "stop your turn, stop your climb, stop your turn."
CNN sought a comment from United early Friday but has not received a response yet.
A near-miss does not cause any injuries but is enough of a close call that the details surrounding such incidents are investigated.
It's also worth noting that the FAA uses the term, near midair collision, for more serious events in which two airplanes come within 500 feet of one another, whereas near miss is a more subjective term.
There were 4,394 near misses in the year ending September 1, 2012, according to an FAA report. Forty-one incidents were characterized as "high-risk events," and none resulted in accidents.
In the year ending September 1, 2011, there were 1,895 such incidents, according to the FAA.
As a result of last month's near miss at Newark Liberty International Airport, the rules for takeoffs and landings at the New Jersey airport were changed.
In that April 24 incident, an Embraer ERJ-145 operated by ExpressJet was cleared to take off on a runway at the same time United Flight 1243, a Boeing 737, was landing on the intersecting runway.
The 737 flew 135 yards away vertically and 50 yards away laterally from the smaller regional jet.
Close calls at Newark had happened before, including four in 2008, according to a Department of Transportation inspector general's report.
There was also a recent incident in Florida in which the FAA confirmed a commercial jet landing at Tallahassee Regional Airport nearly collided midair with a drone. It was so close, the jet pilot thought the two aircraft had collided.
In October, the pilots of a pair of 747s, carrying more than 1,000 passengers, misinterpreted air-traffic control orders and came within 100 feet of colliding over Scotland. A former FAA crash investigation chief told CNN, "Everybody got it wrong."
CNN's Eliott C.McLaughlin and Aaron Cooper contributed to this report.
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