Canadian air traffic controllers are buying pizzas for their American counterparts as a show of support during the U.S. government's partial shutdown.

Nav Canada's national media manager Ron Singer says the initiative began when employees at Edmonton's control centre took up a collection to buy pies for controllers in Salt Lake City, Utah, and Anchorage, Alaska.

All seven of Canada's control centres and many towers have since joined in and ordered pizzas for their U.S. counterparts working along the border, many of whom have taken to social media to express their gratitude.

Singer says there's a bond between Canadian and American air traffic controllers since the two work closely together to manage cross-border airspace.

Some 10,000 air traffic controllers in the United States have been working without pay since late December due to the ongoing government shutdown.

Their union filed a lawsuit in federal court in Washington on Friday, asking for an order compelling the government to pay them what they're owed.