Check out the companies making headlines after the bell:

Shares of RetailMeNot skyrocketed 49 percent in extended trading Monday after the Austin-based coupon site said it will be acquired by Harland Clarke Holdings. The market and retail company is set to pay $11.60 per share in cash for the outstanding shares of RetailMeNot Series 1 common stock at an equity value of $630 million, according to a RetailMeNot press release.

United shares dropped nearly 1 percent after the airline forcibly removed a passenger from a flight. A 30-second clip circulated on social media shows a man being dragged by security after refusing to leave an overbooked flight. He was randomly selected, among 3 other passengers, after no one volunteered to get rebooked on another flight. United's CEO Oscar Munoz said "this is an upsetting event to all of us here at United," and he apologized for the need to re-book customers. He said, "our team is moving with a sense of urgency to work with the authorities and conduct our own detailed review of what happened."

Shares of J.B. Hunt Transport Services sank over 2 percent after competitors Swift Transportation and Knight Transportation announced a merger. The combination of the two truck companies will be worth over $5 billion.