Orbitz's shares shot up 20 percent to $11.63 in morning trading, short of Expedia's offer of $12 per share. Expedia's shares rose nearly 13 percent to $88.50. Priceline shares were up 2.8 percent.
While Priceline's market capitalization of about $55 billion is much more than that of Expedia's and Orbitz's put together, Expedia only recently slipped behind Priceline to become the world's second-largest travel services company by bookings.
The possibility of antitrust issues was played down by Expedia's Chief Financial Office Mark Okerstrom who said, "It is a $1.3 trillion industry and is highly fragmented ... We are only a small player and our overall share is in single digits."
RBC Capital Markets analyst Mark Mahaney said regulatory hurdles would not be significant, adding he believed Orbitz has been one of the weakest players in the industry.
Expedia, which owns Expedia.com, its flagship online travel agency and hotel booking site Hotels.com, has expanded rapidly by buying Travelocity last month and the Wotif Group in November.
"We are attracted to the Orbitz Worldwide business because of its strong brands and impressive team," Dara Khosrowshahi, chief executive of Expedia, said in a statement.
Orbitz, the operator of CheapTickets website, was exploring a sale and had engaged a financial adviser to reach out to potential buyers, Bloomberg reported last month.
Expedia said it expects the Orbitz deal, which has an enterprise value of $1.6 billion, to add 75 cents to earnings and generate cost savings of $75 million.
The equity value of the deal is based on about 115 million Orbitz shares outstanding as of Dec. 31.
Orbitz on Thursday also reported a 37 percent rise in quarterly profit as gross bookings increased to $2.74 billion from $2.48 billion.
Orbitz' results come a day after TripAdvisor, a travel review website operator, also reported an increase in net income as leisure and business travel increased in the United States.