Air Canada and other airlines are allowing some passengers flying through Brussels to rebook their flights for no additional charge, following Tuesday's double bombing at Belgium's Zaventem airport.

Air Canada customers who bought a ticket involving travel to or from Brussels between March 22 and March 28 will be allowed to change their flight at no cost. The new flight must take place before April 30, and must have seats available in the same cabin as the original flight in order to avoid additional fees.

An Air Canada spokesman said this is a "normal policy when uncontrolled or unforeseen events disrupt or threaten to disrupt our schedule."

A spokeswoman for Transat Tours Canada said Transat has no flights to Brussels until late April. But Transat said it will let passengers who missed flights from Charles de Gaulle Airport in Paris and Gatwick Airport in London on March 22 or 23 to take standby flights for free, depending on availability.

American Airlines is giving travellers a similar option, offering to waive ticketing fees for customers travelling to or from Brussels between March 22 and March 29. American is also offering changes to flights to and from Amsterdam, Dusseldorf, Frankfurt, London, and Paris.

Delta Airlines is also offering free ticket changes for passengers travelling to, from, or through Brussels, Amsterdam, or Paris between March 22 and March 31.

At least one guided tour agency is also letting customers in Canada and abroad reschedule their trips. Globus, which operates the Cosmos, Avalon Waterways, and Monograms tour brands, says travellers who were planning to take a tour or cruise that includes Brussels through April 22 may change their departure date to later this year, or next year if necessary.

A common practice

Allowing airline passengers to rebook their tickets for free under certain circumstances is a common industry practice, according to Rick Erickson, managing director of Calgary-based aviation consultants RP Erickson and Associates.

"Essentially, they're saying 'look, we're people too, and this is how we'd like to be treated,'" said Erickson. "It's a goodwill gesture, one of the few times that the carriers are so easy on that goodwill front."

"All carriers have little choice, because there are a number of unknown variables over the course of a year," added Erickson, citing the 2010 eruption of the Eyjafjallajökull volcano in Iceland as a good example.

Britain Ash Cloud Detector

The 2010 eruption of Iceland's Eyjafjallajökull volcano disrupted air travel around the world. (Brynjar Gauti/Associated Press)

Inclement weather is by far the most common reason that airlines would let passengers rebook their tickets without having to pay switching fees, said Erickson, followed by unforeseen events like terrorism or public health concerns.

Zaventem airport near Brussels will remain closed through at least Thursday, as a forensic investigation into the bombings continues.