F-4 Phantom II fighter jets are legendary. They were so powerful that pilots could film missiles accelerating at Mach 1 at 35,000 feet from within them. But with such power comes great devastation. That was the case when two Phantom fighters crashed during a training session near Japan in the 1990s. The damage was so extensive that DNA testing was required to confirm the identities of the two fighter pilots from their remains recovered from the bottom of the ocean.
A fatal plane crash
The McDonnell Douglas F-4 Phantom II is a two-seater, twin-engine, all-weather, long-range plane. It is regarded by many to be one of the best military aircraft designs of all time. The legendary F-4 Phantoms were developed for the US Navy in the late 1950s. They were later adopted by the US Marine Corps and Air Force. Although they have been retired from service in the US, they are still in use elsewhere around the world.
As with any aircraft, several accidents have occurred during the extensive pilot training period required for the F-4 Phantoms, and during armed combats.
The worst non-combat accident occurred in 1971 when an F-4 Phantom crashed into a passenger flight over southern California. The radar intercept officer who ejected from the F-4 Phantom and parachuted to safety was the only survivor. All 49 passengers and crew on the passenger flight perished, along with the F-4 pilot.
Confirming the identify of the pilots
Another devastating incident took place in the late 1990s. A crash between two training F-4 Phantoms near Japan resulted in the traumatic death of both pilots.
Their bodies were crushed in the crash, and disintegrated as they fell into the ocean. This prevented the identification of the bodies using the traditional methods of dental records and body features. Instead, DNA tests were used to confirm the identity of the pilots from the 33 samples recovered from under the sea.
Blood typing as a preliminary analysis
Blood typing is a useful technique for the preliminary analysis of unknown remains and bloodstains. A person’s ABO blood group is usually determined by looking at the presence of different antigens on the surface of red blood cells. But, this technique is not as accurate when samples are degraded.
Genetic analysis of the blood type specific glycosyltransferase gene is an alternative approach for determining blood type, which was used for the analysis of the plane crash victims (referred to as Pilot 1 and Pilot 2).
The parents of Pilot 1 were typed as OO and BO, while the parents of Pilot 2 were AB and OO. Several human fragments from the crash site were typed as BO (one possible blood type for Pilot 1). The other tissue samples were AO, which was expected for Pilot 2 based on his parents. However, blood typing is only useful as an initial analysis to exclude possible identities. Further analyses are necessary for more conclusive results.
DNA analyses for more conclusive results
To confirm the identity of the two pilots, researchers turned to autosomal STR (short tandem repeat) analyses. Autosomal STRs are useful for identifying unknown remains, because only a small region of DNA needs to be analyzed.
We inherit autosomal chromosomes from each of our parents. Therefore, a child’s profile will be a mix of both of the parents’ autosomal chromosomes. DNA profiles were generated using nine STR markers from the tissue samples and the parents of the missing pilots.
In both cases, the STR profiles from the tissue samples matched a profile that is expected for a child of each of the two parent, supporting the blood typing analysis.
Researchers took it another step further looking at mitochondrial DNA (mtDNA) profiles. MtDNA is different from autosomal DNA, because it’s strictly maternally inherited (passed from mother to child). There are hundreds of copies of the mtDNA DNA in each of our cells, making it very useful for the analysis of degraded tissue samples.
Three regions of the mtDNA genome can be used for analysis: the two non-coding regions called HVR1 and HVR2 and the coding region. The HVR1 region was sequenced from the tissue fragments, as well as the parent samples.
As expected, the mtDNA profile from tissue samples that were assumed to be from Pilot 1 matched the mtDNA profile of the mother of Pilot 1. Tissue fragments assumed to be from Pilot 2, generated a mtDNA profile that matched the mother of Pilot 2.
Together the blood type genotyping, autosomal STR analyses and mtDNA sequencing confirmed that the remains recovered from the sea belonged to the two pilots who perished in the horrific midair plane crash.
The need for reference samples
This study illustrates the usefulness of DNA analyses for accurately identifying fragmented, destroyed or degraded human remains, when typical identification techniques (e.g. dental records, body features or Y-rays) are not possible.
As part of this study the mtDNA profiles of the two training F-4 fighter pilots were determined. If you have taken the DNA Maternal Ancestry Test, you can compare your DNA to see if you have descended from one of the same maternal lineages.
In order to confirm the identity of these pilots, it was also necessary to analyze DNA samples collected from their parents. However, if stored DNA samples had been available for the two pilots, a direct comparison between the stored samples and the fragmented remains. This would have provided faster and even more conclusive results.
It’s now becoming increasingly popular to bank DNA samples for testing at a later date. Such applications include saving DNA for disease testing for the benefit of future generations, saving DNA for identification purposes in the event of disaster, or saving DNA to preserve the integrity of the family tree and for inheritance purposes to conclusively determine biological relationships. More information about DNA banking can be found at www.securigene.com.