Nostalrius Begins - Quality wow vanilla realm (1.12)

I have a 33 hunter, and I was on the zep from org to UC tonight. I was not pvp flagged. There was a group of about 5-6 lvl 60 pvp-flagged allies on the zep who promptly ganked any lowbie that got on, but most were not pvp-flagged so they couldn't do anything. However, as soon as the map cutscene was over and the zep was in tirisfal glades, EVERYONE was somehow pvp-flagged and the allies ganked the whole zepload.
Why would I become pvp-flagged when traveling on the zep from one horde territory to another? Isn't this an exploit, and thus bannable (or at least suspendable)? Any GM's have an opinion?

Every horde know risk of zeppelin travel. Travel by water or land if safety #1.

That's hillarious!

The Sea is considered a contested territory, by passing it, you are passing contested territory, therefore you are flagged.