Singapore Airlines.

Singapore and Delta came within 60 metres of each other over Houston, USA. Photo: Reuters

US Federal Aviation Administration (FAA) authorities say air traffic controllers at a Houston airport averted a potential midair collision of two planes.

The incident happened on Thursday night 16 kilometres northeast of Bush Intercontinental Airport, when a Singapore Airlines 777 jumbo jet and a Delta Airlines A320 came about a half-mile (800 metres) horizontally and about 200 feet (60 metres) vertically of each other.

Federal guidelines say aircraft should be separated a half-mile (800 metres) vertically and three miles (4.8 kilometres) horizontally.

FAA's Lynn Lunsford told the Houston Chronicle that an air traffic controller noticed the danger and gave pilots instructions.

Lunsford says they have taken steps to ensure flight crews are aware of the guidelines.

In May, the FAA was investigating an incident in which an air traffic controller's mistake put two planes on a collision course.

AAP