Airlines on Monday waived fees for travelers trying to delay and rebook trips to Las Vegas, as one of America's most popular vacation spots reeled from a horrific mass shooting and saddened travelers weighed their options.

The number of people flying into Las Vegas has climbed as the economy improves, with the city's McCarran International Airport reporting a record 4.3 million passengers in July. The shooting, however, could make some travelers reconsider their plans, at least in the coming days.

"Vegas is a place where you can usually take your mind off of things, and it's kind of hard to do things like that right now," said Clarence Tam of San Jose. He is scheduled to attend a tech conference in Las Vegas next week and is now unsure whether to attend. His fiancee has even asked him not to go.

"I don't know how people are going to enjoy themselves," said Tam, 34.

McCarran airport was briefly locked down early Monday following Sunday night's mass shooting, which erupted at a concert site near the runways.

The brief closure, however, did not appear to cancel or delay any flights from San Francisco International Airport, said SFO spokesman Doug Yakel. Four airlines - United, Southwest, Virgin America and JetBlue - offer direct flights from San Francisco to Las Vegas, with an average of 25 flights from SFO to McCarran each day.

The details on how Tam and other travelers might change their flights varied.

United Airlines waived the flight-change fee for anyone scheduled to fly to or from Las Vegas from Monday, Oct. 2, through Friday, Oct. 6. The airline also will waive any difference in fares between the new flight and the one originally scheduled, so long as the traveler books the same cabin as before, doesn't change any of the cities on the trip and flies by Oct. 13.

American Airlines, in contrast, waived the change fee for anyone scheduled to fly to or from Las Vegas on Monday and Tuesday of this week, so long as those people can still travel by Friday.

Virgin, now part of Alaska Airlines, will waive the change fee and difference in flight price for anyone who had been scheduled to fly Monday or Tuesday, as long as they agree to fly by Sunday. Those who simply cancel their plans can request a refund.

Southwest agreed to let travelers who were booked to fly to or from Las Vegas on Monday "adjust their travel plans without additional cost," said spokeswoman Emily Samuels, in an email. The offer does not extend to the rest of the week.

JetBlue will waive the change fee and fare difference for people scheduled to travel to or from Las Vegas Monday or Tuesday, if they fly by Saturday.

It remains to be seen whether Las Vegas hotels will follow suit and waive cancellation fees. MGM Resorts International - which owns many of the city's largest hotels, including the Mandalay Bay, location of the alleged shooter in Sunday night's attack - did not address the issue on Monday. The company did, however, provide counselors for guests and employees, set up transportation to help guests visit the injured and created a hotline (888-634-7111) for the families of guests to arrange airfare and hotel accommodations.