Consumer laws and airline policies often entitle passengers to receive compensation from carriers when flights experience major delays or cancellations. But few jilted passengers file the paperwork to claim what they deserve. Enter, Kayak, the travel price-comparison search engine. Quietly for the past few months, it has been using its marketing heft to let consumers know they may be able to either receive cash or vouchers redeemable for future travel. When a traveler’s flight has been disrupted, Kayak sends an email notification that says, “Good news: You could get compensation.” It then encourages the traveler to try one of two claim compensation firms — AirHelp or Service — to process their claim quickly.