Did you watch the Arsenal of Democracy flyover on May 8th? If you did, then you saw one of the WW2 fighters, the TBM Avenger, peel off from formation as it was coming over the city and head south. The pilot of the TBM Avenger had to conduct an emergency landing at Reagan National airport due to a hydraulic fluid leak. He posted a video of the event on YouTube. It's pretty interesting.
In the video, you can see the pilot open the canopy wider as what appears to be smoke starts to fill his cockpit. The pilot thought his passenger had passed out (in fact, the passenger was looking at what he thought was a fire).
"A 1500 psi pinhole hydraulic leak vaporized in the cockpit, appeared like smoke, and prompted a decision to abort the flyover and land at Reagan DCA airport," text accompanying the video says