With the thought in mind that there is strength in numbers – or, at least, having an extra set of eyes – U.S. lawmakers have reached out to the travel sector asking for help in preventing another attack in Washington on Inauguration Day similar to what happened at the U.S. Capitol.

Heightened security is the theme of the week as Joe Biden prepares to be sworn in as the 46th President of the United States on Wednesday, Jan. 20. Already, most travel entities have erred on the side of caution, with Airbnb going as far as blocking reservations in the Washington D.C. area this week.

Now, the House Oversight Committee has sent letters to more than two dozen travel-related businesses asking for assistance “identifying and preventing the ongoing and extreme threat of further violent attacks” in Washington and elsewhere, according to CNN.

Letters went to bus line operators, rental car companies and hotels. The request said the rioters who attacked the Capitol on Jan. 6 “relied on a range of companies and services to get them there and house them once they arrived.”

CNN noted the letter asks the companies to increase security and screening of guests and keep business records available for future investigations, as well as provide Congress with records of any policies “currently in place or being developed to ensure that your services are not used to facilitate violence or domestic terrorism.”

The bus companies include Greyhound, Megabus, BoltBus, Lux Bus America, Vamoose, Jefferson Lines, Peter Pan, Flixbus and RedCoach.

Rental car companies who received a letter were Enterprise, Hertz, Avis, National, Alamo, Budget, Dollar and Thrifty.

And the hotels included Expedia (owner of VRBO), Intercontinental Hotels Group, Accor Group, Hyatt, Hilton, Choice Hotels, Marriott, Best Western International, Wyndham Hotels & Resorts and Extended Stay America.

Airlines such as Delta have stepped up as well, banning checked firearms.