The O-Train Line 4, also known as the Airport Link, is a diesel light rail line on the O-Train network in Ottawa, Ontario.

However, these plans were discarded due to lack of funding and a focus on attracting ridership from the south of Ottawa.

[2] In 2016, the Ontario provincial government committed $1 billion to O-Train expansion, providing half the required funding for an extension to the airport, with an additional station at the EY Centre.

[4][9] The line currently uses the Alstom Coradia LINT 41 diesel light rail trains.

The difference in length is due to the use of single-car trains instead of two-car vehicles, because of the line's lower projected ridership.