This free – yes free – mobile app is quickly becoming utilized at most major airports and saving travelers, and customs agents, tons of time.
I always look over at these short lines enviously as people are expedited through the customs process.
Enter the Mobile Passport. All U.S. travelers are welcome to download the app, enter their passport information, answer the same questions you would be answering on the kiosk machines or the paper form, and get in a shorter line than the normal customs line. At JFK airport in New York, passengers sometimes waited over three hours in the standard customs line, while those arriving at LAX could wait up to 3 hours and 41 minutes in the standard line.
Collected and summarized from the source below by Minh Pham https://www.travelpulse.com/news/airlines/mobile-passport-a-growing-app-to-help-beat-long-customs-lines.html