Qantas engineers say they are still no closer to reaching an agreement with the airline after the first day of talks to resolve their ongoing industrial dispute.

Both parties are trying to bring an end to the deadlock at Fair Work Australia in Melbourne after Qantas grounded its fleet and the industrial umpire stepped in.

The airline has 21 days to resolve its differences with three unions: the Australian and International Pilots Association (AIPA), the Transport Workers Union (TWU) and the Australian Licensed Aircraft Engineers Association (ALAEA).

If a deal cannot be reached they will face compulsory arbitration.

But ALAEA secretary Steve Purvinas says he is not sure whether the dispute can be resolved in that period.

"I can't say that we were any closer to an outcome as we speak," Mr Purvinas said.

"I said at the start of the day that we've got a 50-50 chance of reaching an agreement through this process, and I still think today that we're at that same stage where we're not really sure whether we're going to get a negotiated outcome or not."

The TWU says it has legal advice that Qantas broke the law when it grounded its fleet late last month, and could try to challenge the Fair Work Australia ruling.

Mr Purvinas said they would rely on the advice of the TWU.

"Certainly if the TWU has got some advice that says that the actions take by Qantas were illegal, we'd want to get our hands on that advice, and we'd assume that it would apply to our association as well," he said.

Qantas insists it has acted lawfully.

Regardless, Federal Workplace Relations Minister Chris Evans says any union challenge to the Fair Work ruling would most likely fail.

"My understanding is they would have to seek an order before the Federal Court to quash the decision, I think that would be a difficult ask. But our advice is that the decision is robust," he said.

A spokesman for Qantas said the airline was confident the conflict would be resolved and that all matters, including pay, were still on the table.

"We are committed to the negotiations before Fair Work Australia and believe that we should be able to reach an agreement over the 21-day period," the spokesman said.

Another round of talks would be held in Sydney on Thursday, Mr Purvinas said.