The Federal Aviation Administration is investigating a near miss involving two jets at Houston George Bush Intercontinental Airport.
The incident took place on May 9, with two United Airlines flights separated laterally by less than a mile, the FAA said.
This follows a similar incident at Newark Airport which came to light last week, fueling a change of rules for take-off and landing at that airport.
In the Houston incident, "the controller issued instructions to both pilots to safely separate the aircraft," according to a FAA statement.
Both planes had recently taken off and the near miss occurred around two miles from the airport.
United flight 601 was departing for Vancouver at the same time as flight 437, headed for Mexico City.
According to news reports, the Vancouver-bound flight was instructed by air traffic controllers to turn right in error, putting the planes on a direct path to each other.
FAA officials said the air traffic controller quickly realized the mistake and directed both planes to separate.
The near miss happened at 9:38 pm local time, and "the FAA has taken steps to prevent any similar occurrences in the future," officials said.
United Airlines spokeswoman Jennifer Dohm said both aircraft correctly operated according to their air traffic clearances.
