Aerial pictures are another way of finding airfields. Some of the things you have to think about using this technique. Airfields - airports - landing fields that are just relatively level fields are hard to distinguish using only aerial photography. To see smaller airfields require a resolution on the order of one inch equals 250 feet (1:250); 1:100 would be better. The higher resolution pictures are definitely preferred.
Sources for aerial photographs is more limited. The USCGS established a program referred to as the National Aerial Photography Program (NAPP) provides a standardized set of cloud-free aerial photographs of the 48 states. This project started in 1987 and updates are periodically done. The program plan calls for updates every 5 to 7 years. These aerial photographs have a one meter resolution. They are taken from aircraft flying at 20,000ft. The other program was the National High Altitude Photography Program (NHAP) operated from 1980 till 1989 when it was replaced by the NAPP. In the mid 1990s, in addition to the existing B&W 1 meter photography, a coverage was made using false color infrared film. Starting in 1998 and continuing was the new series offering 0.25 meter resolution. The majority of this series uses color film though some areas are in B&W. These color high resolution pictures cover large metropolitan areas. I don't know if the plan is to photograph the entire USA at this resolution or not.
These charts, from NOAA, show the different periods that the NAPP program has photographed the US.
There are commercial sources of satellite pictures. The Russians also sell some of there reconnaissance spy satellite picture too. Since you have to pay for these, I generally don't find them of interest. Free is a better price. The earlier ERTS and LANDSAT pictures are very low resolution satellite pictures and are of limited or no value.
Older photographs are available from the National Archives and Records Administration in the Cartographic and Architectural Branch (located at 8601 Adelphi Road, College Park, MD 20740 - 301-713-7040). The Library of Congress also maintains a large collection of historical photographs, principally from 1900 to the 1940s. This collection is located at the Prints and Photographs Division in the James Madison Memorial Building, 101 Independence Ave., S.E., Washington, DC 20540 - 202-707-6394.
The NAPP aerial photographs have been digitized and are available on the Internet. This includes the baseline B&W 1 meter series and some of the 0.25 color pictures (referred to as Urban Area pictures). You can also buy these as hardcopy prints from the USCGS. The digitized data base is available (open access) on the Terraserver. The Terraserver data base uses pictures taken on all coverages. You can even find some airfields with a split running through them with one picture taken in 1992 and the other half taken in 1996! On one, Louisville, KY airport, you can tell that the airfield had put in a new taxiway that is cut off on the older picture when it did not exist.
In researching for an airfield, Terraserver is invaluable for looking for them or there remains. For old airfields that are inactive/closed, you hope to find remains. The Terraserver has available the NAPP program aerial pictures of the USA. These aerial pictures are in B&W and generally can zoom into 1 meter resolution level. Starting about 2000, a new series of "urban" aerial pictures were started. The nice feature of Terraserver allows you to switch between the aerial picture and the current USCGS topographic map of the location. Depending upon your zoom scale factor, you can get topographic maps down to 1:50,000 or 1:62,500 resolution (highest) quads and zoom out to 1:250,000 scaled charts. Generally, there are three levels of topographic maps; 1) 1:250,000; 1:100,000; and 3) 1:62,500 scales. Might mention that there are holes in the Terraserver data, both aerial photographs and topographic maps at best resolution. The holes in the Nevada area are "military sensitive" areas (Area 51 and others). Sometimes there are holes for no good reason other than I guess they did not have good pictures. Why there are holes in some of the topographic data is unknown. Could be problems with the server or the maps have not been digitized yet. You can download the aerial picture or map section you are viewing if you wish.
Aerial photographs are great for looking to see what an airfield/airport looks like. Terraserver is the largest by far. However, there are a number of specialized aerial photograph websites out there too. There is a program called GIS (Geographical Information System) that is being widely adopted as a standard. Under this program, organizations are establishing websites that contain aerial and other data for specific locals. Some even have historical coverage. For those in Michigan around Detroit, a great one is the Wayne State University coverage from 1949 to 1997. For the Dallas-Fort Worth area, the NCTCOG.ORG has current coverage of that region. NOAA also has a website you can use to find some aerial coverage. The USCGS also has a website that you can use. It is the USCGS Geospatial Data system. The location is the Geospatial Data, Information, and Related Products page. Go down on this page to the Aerial Photographs section and there are choices there. At no cost to you, you can get online to it with an ID and password. You can find not only the B&W coverage available on Terraserver (preferred) but during the mid 1990s, the USCGS NAPP and NHAP programs did a coverage of the USA using color infrared film. Referred to as CIR (for Color Infrared), this uses false colors for temperature of things. An example is green grass and plants will come out red on the pictures.
Some states have used aerial photography for various usages and these photographs can be accessed. Not much is online so you would have to go to a library or Government agency that has them. Some of these aerial photographic projects were conducted by a state's agricultural agency! Florida is a good example where they used aerial photographs for agricultural monitoring.
Another tool is the Acme locator. This is a front end tool for the Terraserver. The advantage that Acme offers is you can type in accurate latitude and longitude (in decimal) and have it find the exact point, including putting a dot on the point. You can use your mouse to out the cursor on a point, click and it will give you that lat and long information. Terraserver has incorporated an improved lat and long entry tool too. For Terraserver, and you click on a point, the lat and long displayed can be off. For most accurate readings, I would recommend Acme. If you are using names only, then Terraserver is the way to go.
A new web aerial pictures system has come on line. This is Google Earth. You need to down load an application (free) and get set up to use it. Once you have the application down loaded, you use it to search the earth of aerial coverage. It has an easy user interface to navigate to locations. While really nice and easy to use, the resolution of the aerial pictures varies greatly from 1 foot resolution to 15 - 25 meters. This data base is made up of various sources and is in color. However, so of the color is actually false color infrared pictures (green plants show up as red). The Google Earth covers the entire world but would suggest that for the continental US, Terraserver and Acme are still best. However, having said that, it would be remiss if did not say that some of the color pictures on Google Earth are more up to-date than those on Terraserver. Google Earth is another good tool to use. There is a feature you can turn on which will graphically depict airfields for you (transportation). I don't know what data base they use for the airfields, but some times, it shows two names for the same field or two slightly different locations for the symbol. Also, the overlays are sometimes a bit off.