Investigators have disclosed that a departing Embraer ERJ-145 crew steered the aircraft at 100kt around another jet which had inadvertently entered the runway during the ERJ’s take-off roll.

The incident occurred at Chicago O’Hare, in darkness but with good visibility, as the Envoy Air ERJ was accelerating along runway 28R.

According to the findings from a US National Transportation Safety Board inquiry, released on 14 April, a GoJet Ailrines Bombardier CRJ700 taxiing for 28R missed a left turn onto the parallel taxiway N and instead proceeded to enter the active runway.

“It was by sheer luck that there was no collision,” wrote the tower air traffic manager in a subsequent communication to personnel. “The result was a near collision that will likely be measured in feet.”

The CRJ700 pilot realised he had entered the runway and immediately turned left, facing the oncoming ERJ, in order to “present the lowest profile”, says the NTSB.

“His primary concern was keeping the tail section of his aircraft away from the runway centerline,” the inquiry adds, and he positioned the jet on the northern edge of runway.

Although an aural alert from the ASDE-X surface-movement and conflict alert system sounded in the tower, there was insufficient time for controllers to order evasive action.

The Envoy Air crew told the inquiry that they had been travelling at about 100kt when they saw the CRJ700 enter the runway, and they steered the ERJ to the left of the centreline in a bid to avert a collision.

Investigators state that the ASDE-X system did not have the positional accuracy to determine the minimum separation distance, but the CRJ700 pilot said the ERJ lifted off as it passed by and he estimated the wing-tip clearance at 15-20ft.

In an air traffic control factual report the NTSB states that GoJet’s policy required at least one pilot to be looking outside the cockpit during taxiing.

But interviews with the CRJ700 crew found that the first officer was “head down” with cockpit tasks and co-ordinating with cabin crew, while the captain had looked down to confirm frequency settings, and incorrectly believed – when he looked up again – that the aircraft was passing taxiway B rather than taxiway N.

None of those on board either aircraft was injured during the incident, on 17 February 2015. The airport’s operator had been in the process of implementing a runway status light system, intended to reduce the risk of incursion, at the time.

Coincidentally the Envoy ERJ-145 (N698CB) was itself involved in an incident at Toronto, two years later in April 2017, when it crossed the hold-short line of the active runway 06L as a United Airlines Boeing 737-900ER was accelerating for take-off bound for Chicago O’Hare. The ERJ stopped at the D3 intersection, where the 737 subsequently rotated.