MONTREAL — Strong bookings have forced Air Canada to reject a request by the federal Liberals for an airplane for the next election, CEO Montie Brewer said Thursday.

"It's very difficult to pull aircraft out of service last minute and use a lot of crew time when we have planes already booked full of customers,'' Brewer said in an interview.

The company reported this week another month of record load factors.

Media reports suggest the Liberals are scrambling to find a campaign plane.

While the Conservatives and NDP have secured arrangements with Canada's largest airline in past elections, the Liberals have flown with other airlines.

In the 1990s, it flew with Canadian Airlines, when it was still operating.

In the last two campaigns, former prime minister Paul Martin's team leased a plane owned by Cargojet president Ajay Virmani.

While Brewer professes not to know the exact timing of a possible election, he said the airline has been given "an idea when things may or may not happen.''

"We've been kind of planning for that but we didn't expect the Liberals to come and ask because they haven't in the past and right now our resources are quite full.''

Liberal spokeswoman Renee Filiatrault wouldn't confirm the party had approached Air Canada but insisted it has other options.

"We'll be able to have the tools that we require Day 1 if (Prime Minister Stephen) Harper forces an election,'' she said in an interview.

With the environment likely to play a prominent role in Liberal Leader Stephane Dion's campaign, the party is likely searching for a more fuel-efficient aircraft than it used in 2004 and 2005.

Filiatrault would only say that the Liberals are looking at ways to "offset carbon emissions with the goal of having a carbon neutral campaign.''

Martin was dogged by questions about his fuel-guzzling election plane -- a 1960s Boeing 727.

The Conservatives poked fun at the Liberal plane, calling it "the high-flying polluter.''

The NDP calculated that the Liberals would use 22,500 litres of jet fuel on a Vancouver-Ottawa flight compared with 13,250 litres for the NDP's Airbus 319.