KLM Royal Dutch Airlines is offering an incentive to get customers to book on mobile — a free external battery with mobile bookings.

Touted on the airline’s Facebook page, users can use their mobile device to navigate to KLM.com or use the KLM mobile app, and then book a flight before December 24, 2013, to get an external battery delivered to your home.

As of this writing, 14,099 flights were booked via KLM mobile as part of the promotion, and there were only 367 batteries left.

Tags: klm, marketing