Air Canada shut down its operations worldwide yesterday when 7,500 members of the International Association of Machinists walked off their jobs after rejecting a contract proposal.

The airline, which operates at least 300 flights to Canada, the United States, Europe and the Caribbean, had just averted a strike two days earlier threatened by 1,700 pilots, who finally agreed to a one-year contract.

The workers who walked out yesterday, the ramp and maintenance employes, had rejected a 25-month contract that would have given them a 16 percent wage increase.

Air Canada's last 13 flights were planes summoned home from Europe crammed with tourists seeking to avoid being stranded while on vacation during the peak travel period.

The shutdown followed a series of wildcat walkouts Tuesday that prompted the airline's executive board to consider closing down operations completely, effectively putting out of work 22,000 employes, nearly 900 of them in jobs in the United States.

Prospects for continuation of contract talks were confused. The head of the Montreal local, to which most of the union's membership belongs, demanded that a meeting scheduled for today be canceled because the membership had lost faith in the negotiating committee.

The union has once previously rejected a proposed contract settlement.

A spokesman for the Montreal local said his members probably would stay out only until today, but the airline's president Claude Taylor, said the company would not resume operations unless it could be assured the union would call an end to sudden walkouts that disrupt service.