As a growing number of airlines prepare to resume more flights in the coming weeks, passengers should expect delays, inconvenience and possibly higher fares.

Safe distancing at check-in queues will lead to messier airports when travel demand picks up, fewer entertainment options will be available in-flight, there will be more rules and health declarations should become more widespread, analysts said.

Exactly how the situation will develop is still up in the air, as airlines await clearer instructions from regulators and governments on coordinated standards.

In a Facebook post earlier this month, Transport Minister Khaw Boon Wan said: "Several proposed measures, from pre-boarding to arrival at destination, are on the table. Like security measures post-9/11, we can expect inconvenience and delay, but public health safety must not be compromised, if we want passengers to take to the skies again."

Experts said a rigorous and lengthy check-in process is likely.

Associate Professor Nitin Pangarkar from the National University of Singapore Business School said: "The new check-in systems will have to do passport and visa checks, ticket checks, baggage weight checks and now temperature checks.

"Longer distance between members in the queue will mean a snaking queue that won't work with today's packed airports."

Mr Nicholas Wyatt, head of research and analysis in travel and tourism at analytics firm GlobalData, said safe distancing at check-in desks will be problematic once flights resume in greater numbers. "The answer here is likely to be the encouragement of - and some airlines maybe even mandating - online check-in processes."

Aviation analyst Mohshin Aziz expects that the authorities will stop people from seeing off their loved ones at the airport, as an additional precaution.

Singapore Airlines (SIA) and other airlines have said the in-flight experience will change, although specifics remain unclear.

Qatar Airways group chief executive Akbar Al Baker, for one, expects a shift in service baseline standards. "The standard of service will drop because you will tailor-make your service to have minimum interaction between crew and passenger," he said.

A few airlines, such as local budget carriers Scoot and Jetstar Asia, said they will seat passengers apart on planes where possible. Other airlines have committed to blocking off middle seats for safe distancing.

Mr Al Baker warned that fares would go up by between 50 and 100 per cent if mandatory safe distancing is introduced.

On how long the airline industry's new normal will last, Mr Al Baker surmised: "All this will change only if there is a robust proven treatment against this virus."

Passengers could also face the prospect of the removal of in-flight entertainment services or even lower carry-on baggage allowance.

For example, Scoot will limit carry-on baggage to 3kg from June 1 to expedite boarding and disembarkation and to minimise congestion as passengers stow baggage. The remainder of the usual 10kg or 15kg cabin baggage allowed will be checked in for free.

Meanwhile, Philippines carrier Cebu Pacific said it will likely start "contactless flights" next month, where passengers will have no physical contact with crew and airline staff. Passengers will have to stow their own bags in overhead cabins, dispose of their own trash and cannot change seats during the flight.

Other airlines - SIA, Jetstar Asia, All Nippon Airways, Emirates, Korean Air, Japan Airlines and AirAsia - said they already have various precautions in place, and will continue to monitor regulations as well as customer sentiment.

The International Air Transport Association (Iata) said in a report last Tuesday that industry measures expected include a push towards self-service check-ins, prepackaged food on board and no queueing for toilets on planes.

It also said large-scale and fast Covid-19 testing to identify infected passengers, which is not yet available, would be a game changer that will reduce the need for multiple precautionary measures. Iata will also support immunity passports that are backed by science and recognised by governments.

The association's Asia-Pacific spokesman Albert Tjoeng said: "It is important passengers have confidence that they can fly safely without contracting Covid-19."

Experts said it is too early to say how the airfares will change.

Prof Nitin said bankruptcy of airlines and social distancing on planes will push prices up, but this is balanced by other factors such as the need to fill seats, lower oil prices and possibly lower airport charges.

While a full recovery in passenger demand for air travel is expected to come as late as the mid-2020s, some rays of hope have broken through the gloomy skies. Travel data provider OAG said in an update on Monday last week that there have been two weeks of growth with airlines adding more flights to increase global capacity by 6 per cent the week before, although capacity is still 73 per cent lower than the same time last year.

Mr Mohshin said it is likely domestic travel will pick up much faster than international travel. He also said that demand for business travel would likely plunge, a sentiment echoed by Qatar Airways' Mr Al Baker.

But business travel agents CWT and American Express Global Business Travel (Amex GBT) said they are confident demand will return.

Amex GBT's vice-president and general manager for Asia-Pacific Joanne Sully said: "The temporary absence of people movement has strengthened the belief that travel is a force for good.

"There is just no substitute for in-person, face-to-face meetings."