Hertz Global ( HTZ) will purchase a smaller, mid-market rival, Dollar Thrifty Automotive Group ( DTG).

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Rental car stocks such as Budget and Dollar Thrifty fell considerably since the attack.

CNN: Car rentals, like airlines, hard hit after attacks

For more than a year, Avis Budget Group and Hertz Global Holdings have been working on deals for Dollar Thrifty.

FORBES: Dollar Thrifty Ends Sale Process, Says Hertz Deal Didn't Eliminate Antitrust Risk

That may be a conservative estimate greater revenue synergies could be driven by expanding the Dollar Thrifty brand overseas, says Wells Fargo analyst David Lim.

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Dollar Thrifty dominated headlines on Tuesday as well, announcing it was ending its sale process as offers it had received failed to eliminate regulatory risk.

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Already, two companies have warned that fallout from the attack will dent their earnings: Dollar Thrifty, which runs the Dollar and Thrifty brands, and ANC Rental, which owns Alamo and National.

CNN: Car rentals, like airlines, hard hit after attacks

Shares of Dollar Thrifty fell 2.6% pre-market Tuesday.

FORBES: Dollar Thrifty Ends Sale Process, Says Hertz Deal Didn't Eliminate Antitrust Risk

Dollar, Thrifty, Hertz and Advantage no longer allow bookings on AutoSlash though you'll still receive price-drop notices.

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Orbitz said it would replace Alamo and National with Dollar and Thrifty rental cars, a decision reached "because it delivered better price points for our customers and better economics for our business, " said Orbitz spokesman Jay Pierce.

CNN: Orbitz, Enterprise car rentals part ways

"Moving forward, we will continue to give to give customers choice among a robust selection of car rental options -- including Hertz, Avis, Budget, Dollar, Thrifty, Advantage and other leading suppliers -- that will fully meet travelers' needs, " the company said in a statement.

CNN: Orbitz, Enterprise car rentals part ways