The union representing 400 striking baggage handlers at airports in Toronto and Montreal says its members plan to picket 24 hours a day until their labour dispute is resolved.

They went on strike at 8 p.m. Tuesday night after contract negotiations broke down between Teamsters Local 419 and Handlex, a subsidiary of Air Transat.

Workers with sandwich boards announcing the strike could be seen marching through Toronto's Pearson International Airport's Terminal 3 and outside the nearby cargo centre on Wednesday. Strikes are also taking place at Montreal's Trudeau and Mirabel Airports.

Teamsters representatives said negotiations ended when the two sides couldn't agree on salaries and bonuses for working night and split shifts. They were the same issues they couldn't agree on during the last round of negotiations a year ago.

"About half of our force does split shifts, so a guy will come in at one in the morning until five, then he might be asked to come back later in the afternoon," explained Amer Khawaja, a worker on the picket line in Toronto.

Union representatives said they took a pay freeze when their contract ended in 2009 in exchange for promises that did not materialize.

A statement released by Handlex said the unionized ramp and cargo employees rejected the company's offer to renew its collective agreement and went on strike.

Handlex responded by locking the workers out and reassigning managers and other employees to ensure operations were not disrupted. So far, flights haven't been delayed, although union representatives say there could be some disruptions on the way.

However, Toronto picketer Harjinder Badial said his colleagues are not trying to cause trouble for travellers.

"We're not here to inconvenience the travelling public, we're just here to get a fair collective agreement," he told CTV News on Wednesday.

Last time the union went on strike, arriving passengers experienced delays getting their bags and some didn't see their luggage for up to a week. That strike lasted 14 days.

The workers are responsible for loading and unloading luggage for several international airlines, including Air Transat, Air France, British Airways and Swissair.

With files from CTV Toronto's Michelle Dube