If it were up to some budget airlines, low-cost travellers at Changi Airport would have to wait longer to check in than those who fly full-service carriers.
While Changi has proven to be a bustling hub for budget air travel, some airlines do not care for its "10-minute rule".
The standard, set by the Civil Aviation Authority of Singapore (CAAS), requires all carriers to ensure travellers do not wait more than 10 minutes, from the time they join the queue, to check in.
Some budget airlines have asked the CAAS to let them bust that limit, arguing that they do not offer the same product and experience as full-service airlines.
The CAAS is reviewing the rule, The Straits Times has learnt.
Changi Airport Group, which runs the airport, and the national consumer watchdog do not think there should be different standards for budget and full-service airlines.
Said the executive director of the Consumers Association of Singapore, Mr Seah Seng Choon: "Why should the standards differ? Budget carriers especially are very strict when it comes to closing time for check-in counters.
"If they take too long to clear people, travellers will end up being left behind. We have had people giving us such feedback."
In just a decade, budget carriers such as AirAsia, Tigerair and Jetstar have gone from zero presence at Changi Airport to accounting for about a third of both travellers and flights currently.
With strong demand for low-cost and regional travel in recent years, budget carriers have been adding capacity and opening up new routes.
The boom in traveller numbers has put a strain on check-in and other resources and, in turn, affects service turnaround time.
To add resources would add to costs, budget carriers said.
Mr Logan Velaitham, who heads AirAsia's Singapore office, said: "Instead of 10 minutes, why not give us 15 minutes? It is a reasonable waiting time, and makes a difference to our costs.
"It is only by keeping our costs down that we can offer our customers low fares and allow more people to travel."
The Straits Times understands that Changi Airport Group conducts regular service checks and tabulates monthly data on the performance of both full-service and budget airlines.
Monetary fines are imposed for failure to meet standards.
Airlines also risk forgoing cash and other incentives the airport gives to promote growth.
Failing once does not necessarily mean penalties are imposed, so the airport does exercise some flexibility, sources said.
Changi Airport Group's spokesman Ivan Tan said: "In situations where standards are not met, our priority is to work closely with our partners to identify the causes and work out solutions for the benefit of our mutual customers."
He stressed that the end goal is to deliver a "consistent world-class experience" to all passengers, regardless of airline and class of travel.
"We take this approach as, within each terminal, passengers enjoy the same amenities and facilities. Similarly, we believe service standards applied in a terminal should be uniform," he said.
Marketing executive Jane Lum agreed. "I fly budget carriers because the fares are attractive, and I understand this means I forgo certain things like complimentary food and drinks. But at the airport, there should be no difference in service standards," she said.
As airports compete for airline passengers, overall efficiency is critical, said Mr Sagar Shahane of industry consultancy Frost & Sullivan.
He said: "The last thing a traveller wants is to be stuck in long lines at check-in, immigration and security.
"One reason Changi is a preferred airport is its efficiency, so these things do matter."