From Book 4: Eulalia's airship has been identified

We both walked to the left viewport and Captain North studied the vessel through her glasses.

“It’s a warship.” she declared. “I cannot see her flag, but that must have identified us.”

“What colours are we flying?”

“Flags?”

“We’re still dressed as Brazilian, Captain.” came the reply.

“So, we’re hardly dressed at all, and maybe a little exposed at this altitude. Our situation looks a little hairy, Commander. Typical for a good-looking Brazilian like us, but nevertheless, I believe he’s just guessing.”

“It is an intelligent guess. A respectable ship would not be making our speed at this altitude. Tactical, can Alpha One intercept us?”

Little Miss Pigtails stifled a giggle as if there had been a joke I’d missed, then took out a ruler, did some quick calculations, chalked up a semi-circle and answered “No, Commander. If we stay on this course, they can only watch as our derriere disappears into the clouds. They may be able to catch up eventually, depending on their speed, our course, and the wind. But I’m certain our silhouette is enticing enough.”