OTTAWA - Government estimates say Canada's air force won't have all its new F-35 fighter jets in place by the time the current fleet retires.

The figures show less than half of the new jets will be on the tarmac by the time the current fleet of 77 CF-18's retire by 2020.

Ottawa has ordered 65 of the radar-evading F-35s.

The delivery of the jets is being spread out between 2016 and 2023 with most of the planes arriving after 2019.

Most of the air force planning over the last decade was focused on getting replacements at least one or two years ahead of that deadline.

Documents obtained by the Canadian Press show an initial delivery of 16 aircraft per year, plus one spare, was expected starting in 2016.

But the latest figures say only 26 planes will be delivered by 2019.

Although the CF-18s won't fall out of the sky in 2020, their airframes and avionics will be worn with age.

The head of the Air Force Association of Canada says Ottawa should upgrade them or buy a handful of the latest version of the fighter known as the Super Hornet.