This is the likely reason. This can also happen if you reply to another member and quote their post in your reply--and their post contains a hyperlink.

Also, FlyerTalk has been hit by an increased wave of spam over the last few weeks, and so the admins have "dialed up" the aggressiveness of the filter that decides whether a moderator needs to approve your post, so even some posts that don't include hyperlinks are being filtered for approval by a moderator.

Don't worry; it'll go away pretty quickly for you.

The "alert a moderator" triangle is there for everyone to help the moderators. If you see a post that needs our attention--is off topic, rude, spam, etc.--just hit it and type a brief explanation and the mods will get an alert to take a peek at it. Sometimes, we can't read every post, so we rely on users like you to help us spot stuff that needs our attention. More on that here.

Maybe if it's not been approved in a few hours...but we already get an alert when a post is caught in the filter, so give us a chance to log in and deal with it.