It boasts that this is a "FREE service that allows you to skip the security queues by reserving a 30-minute slot ahead of your arrival." View 3 Images London Luton Airport offers a pre-book security time slot service (Image: John Lamb / Getty)‌Prebook Security is first-come, first-served. If you use Prebook Security, LLA says they cannot guarantee how long it will take to complete security checks through the Airport Security area. Upon entry to the security area, head to the left where you'll find signs for "Prebook Security". ‌To change or cancel your Prebook Security booking, use the “change” or “cancel” option on your booking confirmation page.