Many BA flights will be grounded during the strike
The Tories have seized on strikes by British Airways and on the railways to claim Britain is facing a "spring of discontent" because of Labour.
RMT rail union members have voted to strike, while Unite members among BA cabin crew will walk out at midnight.
Shadow transport secretary Theresa Villiers urged Gordon Brown to do all he could to call off the BA strike.
A spokesman for the PM said Mr Brown believed the strike was in "no-one's interest" and should be called off.
It would "cause unacceptable inconvenience to passengers", the spokesman said.
"[Mr Brown] urges the strike be called off immediately. He also urges BA's management and workforce to get together without delay to resolve what is a dispute about jobs and wages."
The British Airways strike is set to start at midnight, followed by a further three-day walkout from March 27, after talks between the Unite union and management broke down.
Ms Villiers said: "Labour's union paymasters at Unite are determined to inflict travel misery on thousands of families. It is disgraceful that they are going ahead with this unnecessary strike.
"Gordon Brown should do all he can to urge Unite - who are funding his general election campaign - to call off the strike. Or he should stop taking their money.
"Britain now faces Labour's spring of discontent with militant unions threatening to bring our railways to a standstill as well. Strike action could leave the country facing a serious transport meltdown."
With an election weeks away, the Conservatives have been trying to conjure up images of 1979's "winter of discontent" which saw the UK crippled by strikes in the dying days of a Labour government.
It has also sought to play up Labour's links with Unite, which is partially funding the party's election campaign. In response, Gordon Brown has sought to distance himself from the dispute, saying it was deplorable.
Transport Secretary Lord Adonis said it was disappointing the talks had broken down.
"This strike is in no-one's interests and will cause major inconvenience to passengers. Clearly, passengers travelling in the next few days will need to check with BA on the status of their flights. I continue to urge both sides to find a negotiated settlement."
Meanwhile 54% of RMT members voted for strike action in a row over jobs and safety.
A spokesman for the Department for Transport said: "We are urging both sides in this dispute to continue talking so that any disruption for passengers can be avoided."
BBC correspondent Hugh Pym said that if the RMT and the British Airways strikes were to happen at the same time it would mean bad headlines for the government.
"Maybe that is backing up their view that they can push it a little bit further, knowing the government may have to intervene," he said.
Liberal Democrat transport spokesman Norman Baker said it was the passengers who were suffering in the rows.
"There is far too much macho posturing and cheap political point-scoring going on on all sides of these disputes. Enough is enough.
"Executives, unions and politicians need to start acting like grown-ups and get this sorted before the public declares a plague on all their houses."