As Gander plans to mark the 20th anniversary of 9/11, a question remains: who can come?

The ceremony is just weeks away, but there's still one big question for Gander's upcoming milestone 9/11 memorial service: who will be able to come?

Shifting public health regulations — and the timing of Newfoundland and Labrador's reopening steps — mean the capacity for the event at the town's arena could be anywhere from 350 to 2,000 people, says Mayor Percy Farwell.

And there's also the matter of international visitors: fully vaccinated Americans can enter Canada without quarantine, and the federal government has announced plans to relax measures for residents of other countries on Sept. 7 if conditions allow.

With so many variables, planning this year's 9/11 commemoration in Gander has been a challenge — and, 20 years after the events of 9/11, this year's ceremony is a big one.

"When we started contemplating this and planning this a couple of years ago, it was obviously going to be a fairly large event with a lot of visitors," said Farwell. "Then of course along came the pandemic and our focus had to shift.

"As the situation with the pandemic and the travel restrictions has evolved, we've been shifting on the fly to to meet whatever the current regulations are or what we expect them to be by Sept. 11."

This year's events include a non-denominational service at the town's arena on the afternoon of Sept. 11, as well as a monument unveiling that morning.

The monument features a piece of World Trade Center steel that was donated to the Town of Gander by New York firefighters in 2011.

Farwell says the town believes some Americans will make the trip to attend next month's ceremony, and the town  has been in contact with others who were hoping to attend but will now send virtual messages, including one from a group of first responders and a choral performance by a Miami school.

Gander's memorial service will be streamed online. Farwell says there's been massive interest in the presentation from national and international media.

Though Gander and surrounding communities have been celebrated in documentaries and on Broadway for their role in housing and feeding thousands of stranded passengers, Farwell says the upcoming service will still be focused on the victims of the Sept. 11 attacks.

"It's a respectful reflection and commemoration of the events that took place during that time, with some attention on some of the good that came out of that as well, some of which occurred here and people have become familiar with," he said.

Gander took in 34 passenger flights and 6,600 people on the morning of Sept. 11, 2001, almost doubling the town's population in mere hours.

The stranded passengers slept for four nights in hotels, schools and people's homes, and were fed every day by local volunteers.

In light of those community efforts, Percy said, planning one or two pandemic-influenced commemorations isn't much of a challenge.

"As the events that happened here in 2001 will confirm, we are capable of pulling some things together on pretty short notice, on a much bigger scale than this."

Read more from CBC Newfoundland and Labrador