The nation currently has only 64 percent of the trained pilots it needs to effectively enforce Canada's sovereignty and respond quickly to threats, as well as take part in international operations with allies, the audit said.

The air force is losing pilots faster than it can train new ones, the report warned.

"We found that Canada's fighter force could not meet the government's new operational requirement, which is to have enough aircraft ready each day to meet the highest NORAD alert level and Canada's NATO commitment at the same time," Auditor General Michael Ferguson said.

The warning comes after the UN aviation agency (ICAO) said in February that a global shortage of commercial pilots looms. It determined that 620,000 new pilots would need to be trained to meet growing demand for air transport by 2036.

Canada currently has 76 F-18 aircraft and more than 1,450 personnel contributing to the country's fighter capability.

In the two years to March 2018, however, the Royal Canadian Air Force lost 40 trained fighter pilots and produced only 30 new ones. Since then, an additional 17 fighter pilots have left or stated their intention to leave.

If the trend continues, Ferguson said, "there will not be enough experienced pilots to train the next generation of fighter pilots."

He also noted a shortage of skilled ground crew technicians, which has forced cuts to the number of flying hours.

The job of maintenance crews is complicated by an aging fleet -- largely purchased in the 1980s -- and a government that is not moving forward on its replacement.

The audit noted that the military expects to spend Can$3 billion (US$2.25 billion) to keep its old F-18s flying until 2032, and has not made any significant combat upgrades to them in the past decade, "making them vulnerable" to enemies.

Prime Minister Justin Trudeau's government cancelled the purchase of new F-35 fighter jets when it came to power in 2015, and then scrapped its own backstop for an interim fleet of 18 Super Hornets amid a trade spat with Boeing, before settling on 18 used Australian F-18s.

Five companies have been invited to submit proposals for an order of 88 advanced fighter jets, which are to be delivered starting in 2025.

Dassault dropped out of the running earlier this month, leaving an Airbus-BAE consortium, Boeing, Lockheed Martin and Saab to bid.