International flight attendants have been offered new Apple iPad Pro's - all paid for by their union. Just, coincidentally, as a union election is under way.

The offer has been dubbed an "iBribe" by a team challenging Michael Mijatov, current secretary of the international division of the flight attendants' union.

And the offer won't come cheap with Mr Mijatov confirming it will cost the union about $2.5 million. That's more than the union's entire annual revenue.

And questions are being raised if the offer is legal.

Mr Mijatov defended the iPad offer saying the union has been well run with $6 million in the bank and has not lifted fees for 12 years and even cut them for some members.

"Other unions are junketeering and spending money unwisely and we know what the royal commission threw up as well," he said.

Bruce Roberts, part of the team challenging Mr Mijatov, said the union's membership had declined and not enough was being done to recruit members or provide services.

"It's a slowly decreasing, decaying union. Our team wants a vibrant future for our union with growth and support for all members."

Mr Mijatov described the iPads as a "really useful tool for flight attendants" and said members would get a vote on whether to receive them after the election.

"Those who say I'm bribing them will get the chance to say yes or no," he said. "They can just say no."

He said the timing of the offer, just before an election, was "fairly coincidental".

Mr Mijatov described his opponents, whose candidate for secretary is flight attendant Teri O'Toole, as "an extreme but militant group with no experience at all".

Mr Roberts rejected those comments and said his group was experienced from wide and varied backgrounds.

But it is not the only time the offer of iPads have coincided with an election at the union.

In 2012 members were also offered a free iPad after Mr Mijatov was challenged by a candidate backed by a Transport Workers Union linked slush fund.

Those iPads - which 88 per cent of members supported receiving - cost the union nearly $1.4 million.

His opponents have raised concerns the offer is not legal.

Unions, under the Fair Work Registered Organisations Act, are not allowed to use their own resources to support a candidate in their own union elections.

The Fair Work Commission would not comment on the legality, or otherwise, of the free iPads.