The Transportation Safety Board says the use of non-standard phraseology in radio exchanges between the crew of an Air Canada Embraer 190 and a ground controller at Pearson International Airport was cited as the primary cause of a serious runway incursion in January of 2016. In a report released earlier this week, the TSB said “plain language taxi instruction” by the controller was misunderstood by the E190 crew and the pilots’ readback using the same language failed to flag the misunderstanding to the controller. The aircraft taxied onto Runway 24R for takeoff as a company A320 was on short final for the same runway. The Airbus crew was half a mile from the runway at 270 feet AGL when they spotted the Embraer and went around.

In the report, the TSB said that instead of using standard phraseology to tell the crew to hold short of the active runway, he instead said: “OK, the nineteen hundred [GGN7286] is still waiting for their video player to finish so he is not ready; you can go to the right side and [switch to frequency] eighteen thirty-five.” The Embraer crew interpreted that as clearance to get on the right runway (24R) for takeoff and responded: “Over to the right side, eighteen thirty-five. Thanks for the help, Air Canada seven two six.”

In its findings, the TSB said the use of standard phraseology is vital to aviation safety. If air traffic controllers are not required to use standard phraseology that reinforces the need to hold short of a departure runway, there is an increased risk of miscommunication leading to runway incursions,” the report said. “If plain-language phraseology used by air traffic controllers is not explicit, there is a risk of miscommunication between air traffic control and flight crews.”