Wikia HT - Laura recapping her situation
Laura, when first met, is a flight attendant pulling a shift with the undercover Winston on the San Francisco - Seattle leg of the journey being taken by the mysterious 'Casper'. We see her in the cockpit, following instructions from Chance as he tries to bring the damaged jumbo jet safely to earth. She's quick-witted and resilient, which helps everyone's chances of survival. Unfortunately, down in the fuselage, it turns out she's also one of the hired guns sent to stop Casper getting to Seattle in one piece.
Wikia HT - Laura's last moments
Chance, however, had already figured this out, and lifted her sidearm without her noticing, leaving 'Laura' with no means to safely complete her contract. Chance tries to offer her a position with the team, but in the end, and unlike him, she can't seem to tear herself away from her old life, much as she hates it, and elects rather to plummet to her doom, perhaps in the hope of giving him nightmares.

She was presumably hired by Nick Chepekian.