Getting shots of vapor is a popular thing when shooting fast jets. An airliner on a damp day can also result in some clouds being formed. While shooting something special at Oakland, I was getting a few shots to make sure the light metering was working as planned. A Southwest 737 came in and, as it flared for landing, it had a nice cloud of moisture form over the wing. Normally these things pop up further out on the approach and don’t make for a good shot but this one was close at hand.