In the ZRCV expansion, the pacific theatre rule (M3) allowed players to call for a rescue craft if the airship was over maritime territory and had to either; make a safe landing or have crew that successfully bailed out of a crashing airship or aircraft. Because failing to rescue crew in the drink results in negative VP, the rescue presents both a challange as well as a way to recover from a crash for the win.
The rescue rule wasn't really available for players running a European Campaign or Scenario as it was only referenced in the ZRCV scenario sheets. This meant that if players were forced to land during a Maritime territory (safe or otherwise), the Zeppelin was considered lost at sea, along with all your crew. (-30VP)
I rummaged through the Sierra Madre Forum and found this reference from Phil that added the rescue option to the European Campaign or scenarios. It's also a good read from a historical view as it's an interesting couple of events. All the below text is by Phil Eklund, the game designer
New Rescue Rule for Airships At War.
M3 RESCUE (additional rule)
If a Zeppelin on a British raid makes a safe maritime landing per D14, and still has its radio, it can call for a German torpedo boat to tow it back to port. Roll 1d6 each segment C1, a 5 or 6 will enter a rescuing German torpedo boat on the map. The German torpedo boat may travel at a speed of four (if not towing), or one (if towing). It is armed with two machine guns. After docking, it tows the Zeppelin, and the German player may attempt to finish up the remaining maritime situation cards at altitude zero.
This rule is inspired by the following history (My thanks to Bruce Dawson, for lending me the Raymond Laurence Rimell book on Zeppelins, from whence this information was taken.)
In August 1916, the Navy L12 (type p) while returning from a air raid over England was struck by the Dover 3 inch naval guns. The ship jettisoned everything available, and tried to stay aloft dynamically, but at 02:40 hours came down in the English Channel. A German torpedo boat was summoned by radio, and by sunrise the Zeppelin was being towed back to Ostend. However, the 2nd Wing of the RNAS stationed at Dunkirk had also been informed, and sent several waves of aircraft to bomb the foundered Zeppelin. A BE2c dropped two Hale bombs and several grenades, but was struck in the fuselage and propellor by machine gun fire from the boat and was driven off. A second RNAS raider, in a Henry Farman bomber, was shot down by the Ostend shore battery. A Bristol Scout also dropped four bombs and a dozen explosive darts from an altitude of 300 meters, but missed in the morning mist. He too was driven off by AA fire. Five more pilots made the attempt over the next two hours, in Scouts, Avroes, and Nieuports, but several of them were hit by flak, and none were able to press the attack upon the Zeppelin at the pier, which was dismantled and salvaged.
While returning from a January 31, 1916 raid over Birmingham, the Navy Airship L19 (type p) came under fire from Dutch guns over Ameland and suffered three engines out and cell damage during the afternoon of the following day. The German commander was able to get his position radioed out before his wireless broke down. Both the Germans and British sent destroyer flotillas to find the airship, but without success. On February 2, however, the British fishing trawler King Stephen stumbled across the L19, now floating in the North Sea 100 miles off the British coast. The German Luftschiff crew had cut off the gondolas to lighten the ship, and from their makeshift encampment on top of the envelope, pleaded for rescue. The trawler captain weighed his options. The Germans outnumbered his crew of eight by two to one, and he was fishing in a prohibited area and was afraid of retribution by the authorities. He left the Germans to their fate, and did not make a report until the next day. By this time, the Zeppelin had sunk, and the only traces of the crew ever recovered were several forlorn messages in bottles. News of this incident leaked to the German Naval Airship Division, who were naturally enraged. On the 25th of April, 1916, the King Stephen was torpedoed by the lead ship of the German 6th torpedo-boat flotilla, and her crew were carried back to Germany as POWs, despite protestations that they were civilians.