When he heard the knight say, "Hold on," Altair stopped. Here we go, he thought. In the future, when they robbed abandoned ancient sites, they would have to remember not to bring law enforcement along.
He put on a look of surprise and turned around to face her. "Theft?" he repeated, and then laughed. "Oh, you thought- well, of course you did. This must look terribly suspicious, the four of us stalking through the sewers like a bunch of- of thieves!" He laughed again, as though the idea that they were thieves was too ridiculous to take seriously. "No, no. You see, this airship hangar is a bit of a family legend. Supposedly it belonged to my great-great-grandfather, an eccentric and paranoid man. It was just a rumor for the longest time: we had no proof it even existed except this old and faded map, which might have been for anywhere.
"In the past week or so, we started hearing rumors of this place again, and a lead that the map might have started here in the sewers. I thought it might be fun to just look, anyway, and so I recruited some of my friends to see if we couldn't find it. I realize we went about this in a rather unconventional manner, but then again, I've always been a bit of a dark chocobo."
He'd been walking while he spoke, and he now stood in front of her. Looking into her eyes, he put all of his Orator skill behind his words in order to Persuade her to believe what he wanted her to believe. "So, you see, we are not thieves. I own this hangar. It has been in my family for years, and we are taking only what is already mine." He smiled, a bit cockily. "If you want to verify, I can make an appointment with my solicitor and we can review the documentation with you."