An aerpplane takes off
An American Airlines airplane takes off from Heathrow airport in London July 3, 2014. Reuters/Luke MacGregor

Had it not for the quick attention and decision of air traffic controllers at Houston's Bush Intercontinental Airport, a midair collision of two commercial airplanes could have happened on Thursday, potentially claiming dozens of lives.

Lynn Lunsford from the Federal Aviation Administration said an air traffic controller noticed the deviation between a Singapore Airlines jumbo 777 and a Delta Air Lines A320 just before 7 p.m. on Thursday. The air traffic controller immediately issued traffic alerts and instructions to both pilots, averting what could have been a midair disaster.

The Singapore Airlines 777 jumbo jet and Delta Airlines A320 was a half-mile horizontally and about 200 feet vertically of each other.

"The FAA is still determining the closest proximity between the two flights," Lunsford said.

FAA guidelines state that aircrafts should be separated a half-mile vertically and three miles horizontally.

The outbound Singapore Airlines 777 jumbo jet took off just before 7 p.m. Central Daylight Time but was found that it "did not level off" at the required 4,000 feet.

The Delta Air Lines A320, meantime, was flying inbound at an altitude of 6,000 feet and preparing to land.

Their almost midair crash scenario was averted by only a distance of eight football fields horizontally.

FAA officials are now investigating the incident. "As a result of a preliminary analysis of the event, the FAA has taken steps to ensure that all flight crews are aware of the top altitudes for standard departure routes," Lunsford said.

A similar incident has occurred at the same state in May when two United Airlines passenger jets came within a mile of each other.

Occurring just after takeoff, United Airlines Flights 601 and 437 flew 0.87 miles apart horizontally and 400 feet vertically from each other.