Air travel, like religion, can come with a lot of rules and restrictions. There are designated times to stand, sit and eat. The seating is often less than luxurious, and the food can leave something to be desired.

And sometimes, the two sets of rules conflict, as seemed to have been the case on a recent Toronto-bound Porter Airlines flight, when a passenger claimed a man who appeared to be an ultra-Orthodox Jew did not want to sit next to her because she's a woman.

Toronto resident Christine Flynn wants an apology from Porter after a flight attendant, who was attempting to remedy the situation, asked if she would be willing to move to another seat. She refused, and the man, who has not been identified, traded seats with another passenger who offered to accommodate him.

Each airline deals with these challenges in its own way and for different reasons, but many were vague when asked by CBC if they have specific rules for dealing with devout passengers. Porter spokesman Brad Cicero said the company has, until now, dealt with issues on a case by case basis, but now plans to establish a more "formal protocol" for its employees.

The recent incident on Porter Flight 121, which had left Newark, N.J., is not the first time that prohibitions among the ultra-Orthodox have led to some last-minute musical chairs aboard a plane, nor are especially devout Jews the only faithful facing challenges when flying.

Here are a few issues that have come up:

Women, seating and cemeteries

A more dramatic incident in 2014, aboard a flight from New York to Israel, drew attention to the challenges of accommodating some ultra-Orthodox Jewish men, who refuse to sit next to women to whom they are not married or otherwise related.

The El Al flight turned into an "11-hour nightmare," according to one passenger, after a group of men, who had earlier tried to switch their seats with other passengers, reportedly stood up and blocked the aisle shortly after takeoff.

The Tel Aviv-based daily newspaper Haaretz had earlier reported that Orthodox Haredim were causing "a host of logistical problems" for the Israeli airline. But despite outcry at home and abroad, El Al said it has no official policy for dealing with religious seating requirements, and no plans to introduce one.

Ultra-Orthodox communities in Israel have also lobbied for gender segregation on buses and in other public spaces.

El Al has seen some ultra-Orthodox passengers seal themselves in plastic bags as protection against the impurity that comes from flying over a cemetery. The airline reportedly banned the bag practice in 2001.

Patting down priests

CBC News revealed last year that Canada Border Services Agency managers at Toronto's Pearson airport allowed a small group of Hindu priests to avoid screening by female border guards to comply with their religious beliefs.

A female CBSA officer said she and her colleagues were outraged that the request by the priests, called sadhus, was even considered by management. Granting such a request threatened to undermine border guards' efforts to prevent criminals, terrorists and illegal immigrants from entering the country, she said.

"People are saying, 'What is next? If white supremacists come through, do we move all non-white officers from the line?'" the officer told CBC.

Another CBSA officer, who, like her colleague, spoke on condition of anonymity, later came forward to confirm similar events, citing an incident five years earlier involving a group of unidentified men in robes who did not want to be searched by women.

Check your dagger, please

Kirpans, the ceremonial daggers that many Sikhs are required to carry, have been the focus of controversies across Canada — not the least of which was an outright ban by a Quebec school board that the Supreme Court overturned in 2006.

The daggers are allowed in some places that don't permit weapons — including Parliament buildings and some courthouses — but don't try to take one on a plane.

Kirpans are specifically mentioned by the Canadian Air Transport Security Authority among the "religious and cultural items" that "should be packed in your checked baggage." They are also banned by the Transportation Security Administration in the U.S.

A Sikh passenger can, however, carry a kirpan on domestic Air India flights, with certain restrictions.

Which way to Mecca?

Among the challenges faced by Muslim faithful while travelling is the requirement to pray five times a day while facing Mecca.

When, for instance, is one supposed to say the midday prayer while on a flight that crosses five time zones?

Luckily there's both an app, and a website, for that.

Crescent Rating, a Singapore-based company that rates the halal services of hotels and other travel services, also offers an app that works out the proper prayer times. The traveller just plugs in the departure and arrival details, and other details including the plane's cruising altitude.

The app tells the traveller when to pray and points them in the direction of Mecca, based on the flight path, using the basic shape of the plane for reference.