The Martin Mars fleetFour US Navy's Martin Mars flying boats fly in formation. Naval History and Heritage Command Founded by aviation pioneer Glenn L. Martin, the Martin Company developed and produced the Mars flying boat fleet for the US Navy. Best known for its contributions to military and commercial aviation, the American aircraft manufacturer was also behind innovative military bombers like the B-26 and B-10, which were widely used in World War II.In the mid-1940s, seven Mars seaplanes were delivered to the Navy, scaled back from the 20 planes the sea service ordered following the end of WWII.The first Mars prototype, dubbed "the Old Lady," was delivered in 1943. It was followed by the cargo variant of the Hawaii Mars, the Philippine Mars, the Marianas Mars, the Marshall Mars, the firefighting variant of the Hawaii Mars, and the Caroline Mars.While most of the fleet has been scrapped, lost, or destroyed over the last eight decades, the second Hawaii Mars and the Philippine Mars survived to this day. The Hawaii Mars was donated to the British Columbia Aviation Museum in Canada, and the Philippine Mars will make its final home at the Pima Air and Space in Tucson, Arizona.The Navy's largest World War II-era aircraftA US Navy sailor assisted a passenger as she disembarked the Philippine Mars. Ted Huggins/Naval History and Heritage Command The Mars flying boats were the world's largest operational seaplanes and the Navy's largest WWII-era aircraft.It measured nearly 120 feet in length and 200 feet in wingspan roughly the size of a modern-day Boeing commercial airplane.After the flying boats were reconfigured from patrol boats to cargo planes, the massive flying boat had a max takeoff weight of over 85 tons or about 165,000 pounds. It could accommodate a 32,000-pound payload, including up to seven military jeeps.Rocket-powered takeoffsThe Philippine Mars taxied in a circle during flight tests above San Francisco Bay. Naval History and Heritage Command Despite its hulking size, the four-engined flying boats had a maximum speed of over 200 mph. The aircraft had a service ceiling of up to 14,600 feet and a range of 4,900 nautical miles.The aircraft were propelled by small rockets known as jet-assisted take-off bottles equipped under the wings. These small rockets provided extra thrust to help them get airborne quicker or take off with heavier payloads.Setting world recordsThe cockpit of the Philippine Mars. Coulson Aviation The Mars seaplanes were operated by a crew of four comprising pilots, engineers, and ground crew. It also had accommodations for a relief team.The aircraft could also transport over 130 fully-equipped troops, or 84 litter patients and 25 attendants.In March 1949, the Caroline Mars, set a world record for airlifting passengers on a single flight, carrying 269 people from San Diego to San Francisco.But the youngest Mars flying boat didn't hold the title for very long a little over two months later, the Marshall Mars broke the passenger load record by transporting 301 people from Alameda to San Diego.A versatile transport aircraftPlumes of smoke erupt behind the Philippine Mars during a rocket-assisted take-off. US Navy Though produced at the latter end of WWII, the Mars fleet supported US Navy operations by flying cargo between Hawaii and the Pacific Islands. The flying boats were later deployed as medical air transport lifts between Hawaii and California during the Korean War.After the Marshall Mars was damaged by an engine fire near Pearl Harbor, Hawaii, the remaining four aircraft continued to transport cargo from San Francisco to Honolulu until 1956, when they were decommissioned and beached at the Naval Air Station Alameda.Aerial firefighterThe Martin Mars aircraft was developed to transport cargo during World War II, later supporting medical air transport lifts during the Korean War. Coulson Aviation After retiring from military service, the remaining Mars fleet, which became known as "the Big Four," was sold to timber companies in British Columbia in the late 1950s, finding a new purpose as the world's largest water bombers to combat forest fires.The four flying boats were modified with large tanks that could carry more than 7,000 gallons of water and up to 600 gallons of foam concentrate, which was used to create a fire retardant to smother the flames. The Mars tankers could make a drop every 15 minutes, loaded with enough water or foam to douse an area of up to 4 acres at a time.Finding a final resting placeThe Philippine Mars' engineering station features panels of controls and gauges to monitor the aircraft's engine and fuel. Coulson Aviation The Marianas Mars crashed in 1961 during firefighting operations in Vancouver Island, and the Caroline Mars was damaged beyond repair by a typhoon the following year.The last surviving Mars flying boats the Philippine Mars and the Hawaii Mars were later acquired by Coulson Aviation in 2007 to "expand its firefighting capabilities," according to the company.The Coulson Group said the aircraft underwent several upgrades and renovations to make it a safer and more reliable aerial firefighter, but officials inLockheed C-130.But after sitting in storage for half a decade, the Coulson Group decided to retire the Philippine Mars in 2012, donating it to the National Naval Aviation Museum in Florida as a permanent exhibit. Its red-and-white paint scheme from its time as a water bomber was replaced with its original dark blue Navy colors, but the trade deal with the Navy was put on indefinite hold amid the 2016 presidential election.Last April, Coulson Aviation announced that the Philippine Mars would instead find its final landing at the Pima Air and Space Museum.As the aircraft's retirement approached, the Coulson Group offered experiences for aviation enthusiasts to get "up close and personal with their Martin Mars water bombers."The program, which had packages ranging from $1,000 to $15,000, featured tours of the planes and the opportunity to observe maintainers working on them. The top-tier experience, which included an opportunity to taxi the plane on the water, sold out in three days.End of an aviation eraThe Philippine Mars was painted a bold red and white when it operated as an air tanker, but its final paint job is navy blue in commemoration of its naval service. Coulson Aviation Over the last few months, multiple attempts have been made to get the Philippine Mars airborne to make the 800-mile flight from Vancouver Island to San Francisco to commemorate its service with the US Navy.After four engine and propeller changes with parts taken from the Hawaii Mars, the Philippine Mars successfully took off from Sproat Lake, making its final flight to San Francisco Bay on Sunday.The next day, it departed the Alameda Seaplane Base and flew to Lake Pleasant, Arizona, where the plane is expected to be de-watered, dismantled, and towed to the museum."Against all odds, the team behind her has worked tirelessly to prepare her for this final journey to Arizona," Coulson wrote on social media. "She may be leaving the water, but her legacy will always ripple through history."