(a train or airplane is) now boarding

When a train, bus, or airplane is "boarding", it means that passengers are being let onto it.

When airport or train station employees are making announcements, they say:

Now boarding.

But when you want to talk about the flight or train that you're taking, you say:

My flight's boarding now, so I've got to go. I'll call you later.

I think our train is boarding.

This phrase appears in these lessons: