Air traffic controllers are worried there could be a major disaster if they're not allowed to take proper breaks.
They want a law change, to enable them to take rest, meal and toilet breaks and warned MPs that the flying public is being placed at risk.
MPs are hearing submissions on the government's employment relations bill, which would restore statutory rest and meal breaks, and roll back changes made to collective bargaining and union rights.
But the Air Line Pilots' Association told them that air traffic controllers are exempt from mandatory rest and meal breaks and says that has considerable safety implications at the country's eight solo watch towers.
An air traffic controller Kelvin Vercoe, who has worked at Nelson and Blenheim airports, described what could go wrong.
"The worst case scenario would be an aircraft calling a mayday while you've got your pants around you ankles," Mr Vercoe said.
"Some of these control towers have the toilet outside the security zone so there are procedures and time involved in getting to the toilet."
Air Line Pilots' Association president Tim Robinson said there's an easy solution.
"So what happens overseas is that generally there's more than one air traffic controller in the tower, that enables those air traffic controllers that have sole watch to have the breaks that's required - that works very, very well."
"We realise air traffic control in New Zealand is an essential service but these air traffic controllers have got to be provided with breaks, to get adequate rest, to get some fresh air even to go to the toilet," Mr Robinson said.
"We think it is [dangerous], we think it's a potential flight safety risk."
But the general manager of air traffic services at the state-owned air traffic controller Airways, Tim Boyle, said that's not fair.
"The chances, as I said ,of an accident occurring as a result of a controller being on a nature break is incredibly, incredibly slim - so I do think the comment is a little bit scaremongering yes."
Mr Boyle said he's a bit surprised the Air Line Pilots' Association even brought the matter up.
"I spend time in those towers - all of those eight around the country from time to time and it's not a topic of conversation, it's not been raised as an issue in any of those visits.
In the regions the reality is that there are long periods of time, 30 to 40 minutes at a time, when there is no traffic - some of these airports are very, very quiet."
The Workplace Relations Minister Iain Lees-Galloway said the government will look into it.
Obviously we listen to all the submissions that come in and we take them into consideration, one of the concerns about having a more stringent approach to rest and meal breaks was that it would not have the flexibility for those emergency services, or services where we need to have people on the desk at all times."
The eight solo watch towers are at Invercargill, Dunedin, Woodbourne (Blenheim), Napier, Rotorua, Gisborne, New Plymouth and Whenuapai airports.