Even though the B-17 was ineligible for a FAA license to carry revenue-paying passengers, several were converted as business or executive transports and used for a while by American corporations. These conversions were essentially similar to the wartime CB-17/XC-108 cargo transport conversions. A few surplus B-17s were even converted into cargo transports with XC-108A-type cargo doors installed.
Several ex-military B-17s were fitted with extra tanks and were used for spraying operations.
In 1960, the first of 23 ex-military B-17Fs and Gs were converted into fire-fighting aircraft. The bomb bay was reconfigured to accept a 2000-gallon tank which carried a water-borate mixture to be dropped on forest fires. The tank was divided into four compartments, each with a quick-opening bottom which allowed the water to be dropped. These planes were operated under contract to the US Forest Service, and a few were still flying as late as 1984.
By the early 1980s, most B-17 water bombers had been grounded, mainly due to the lack of Wright R-1820 Cyclone engines. One water-bomber operator solved this problem by installing Rolls-Royce Dart turboprop engines in place of the Cyclones. This was done for B-17G Air Tanker N134ON. N1340N crashed in October of 1970, when fire smoke caused engine failure in the Dart turboprops.
The Institut Geographique National of France operated thirteen B-17s during the post-war years to perform worldwide survey and geophysical research missions.
USAAF Serial French civil Disposition 42-30177 F-GBSG used for spares, scrapped 1973 42-32076 F-BGSH currently on display at WPAFB Museum 43-39304 F-BDAT Destroyed in 1950. 44-8846 F-BGSP Still flying in France 44-8889 F-BGSO on display at Musee de l'Air 44-83728 F-BGOE scrapped in 1970. 44-83729 F-BEED scrapped in 1962. 44-83735 F-BDRS with Imperial War Museum. 44-83757 F-BDRR scrapped 44-85594 F-BGSO scrapped in 1972. 44-85643 F-BEEA destroyed in 1989. 44-85718 F-BEEC with Lone Star Flight Museum 44-85733 F-BEEB destroyed 1949. 44-85784 F-BGSR with B-17 Preservation Ltd.
In 2020 the Aero Vintage Books website listed 47 surviving intact B-17s. Of these, nine are currently operational and flown at least occasionally. Another twenty-five are on static display and available for public viewing. Several of those have been flyable in the past few years, but appear to be grounded now for various reasons. Nine B-17s are under some form of restoration and five B-17s are in storage. The partial remains of at least five B-17s are also held. For the most part, these examples are in storage and may form the basis for future restorations.
Another 27 B-17 airframes are believed to be in known locations at crash sites throughout the world, and may be recovered in the future.
Today, the only B-17s still flying are those that are used by such organizations as the Experimental Aircraft Association, the Collings Foundation, and the Commemorative Air Force as "flying museums".
A list of surviving B-17s can be found at the Aero Vintage Books website, which can be accessed by clicking here. It draws heavily from the book Final Cut by Scott Thompson. You might want to check this site for frequent updates. Also listed there is a table of all B-17s that have had civil registrations over the years.