Accurate airport operations counts are important for determining appropriate funding allocations for airport development and improvement. Fewer than 270 of the 2,950 non-primary airports in the United States, however, have air traffic control (ATC) personnel who are available to count airport operations. Existing counting methods such as automatic acoustic counters (AAC) are not viable long-term solutions because of the expense and inconvenience of deploying the devices on a large scale. This paper validates a cost-effective counting technology based on a technique that uses signal strength obtained from aircraft transponders to register the occurrence of aircraft operations at non-towered airports. Over 50 million transponder records were collected from two different versions of the system, which were installed at Purdue University Airport (KLAF), Terre Haute Regional Airport (KHUF), and Indianapolis Executive Airport (KTYQ), all in Indiana. The operations counts calculated from these records were compared with those obtained from the Federal Aviation Authority (FAA)’s Air Traffic Activity Data System (ATADS) database, which contains official operations data reported by airports with ATC towers. The Version I device utilized a Raspberry Pi platform and produced error rates ranging from −10.2% to +7.6%. The Version II device consisted of the pre-production commercialized system and resulted in error rates ranging from −4.9% to −1.4%. The test results suggest that this pre-production implementation of the transponder signal-counting technology is an accurate and cost-effective way to count non-towered airport operations. Improvement and testing of this technology is being undertaken, and field deployments are ongoing at additional airports.

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