Amelia Earhart - Wikipedia

On July 2, 1937, Amelia Earhart and Fred Noonan disappear flying over the Pacific Ocean. From the article:

"During Earhart and Noonan's approach to Howland Island, the Itasca received strong and clear voice transmissions from Earhart identifying as KHAQQ but she apparently was unable to hear voice transmissions from the ship. Signals from the ship would also be used for direction finding, implying that the aircraft's direction finder was also not functional.

The first calls, routine reports stating the weather as cloudy and overcast, were received at 2:45 and just before 5 am on July 2. These calls were broken up by static, but at this point the aircraft would still be a long distance from Howland.[157]

At 6:14 am another call was received stating the aircraft was within 200 miles (320 km), and requested that the ship use its direction finder to provide a bearing for the aircraft. Earhart began whistling into the microphone to provide a continual signal for them to home in on.[158] It was at this point that the radio operators on the Itasca realized that their RDF system could not tune in the aircraft's 3105 kHz frequency; radioman Leo Bellarts later commented that he "was sitting there sweating blood because I couldn't do a darn thing about it." A similar call asking for a bearing was received at 6:45 am, when Earhart estimated they were 100 miles (160 km) out.[159]

An Itasca radio log (position 1) at 7:30–7:40 am states:

EARHART ON NW SEZ RUNNING OUT OF GAS ONLY 1/2 HOUR LEFT CANT HR US AT ALL / WE HR HER AND ARE SENDING ON 3105 ES 500 SAME TIME CONSTANTLY[160]

Another Itasca radio log (position 2) at 7:42 am states:

KHAQQ CLNG ITASCA WE MUST BE ON YOU BUT CANNOT SEE U BUT GAS IS RUNNING LOW BEEN UNABLE TO REACH YOU BY RADIO WE ARE FLYING AT A 1000 FEET[161]

Earhart's 7:58 am transmission said she couldn't hear the Itasca and asked them to send voice signals so she could try to take a radio bearing. This transmission was reported by the Itasca as the loudest possible signal, indicating Earhart and Noonan were in the immediate area. They couldn't send voice at the frequency she asked for, so Morse code signals were sent instead. Earhart acknowledged receiving these but said she was unable to determine their direction.[162]

In her last known transmission at 8:43 am Earhart broadcast "We are on the line 157 337. We will repeat this message. We will repeat this on 6210 kilocycles. Wait." However, a few moments later she was back on the same frequency (3105 kHz) with a transmission that was logged as a "questionable": "We are running on line north and south."[163] Earhart's transmissions seemed to indicate she and Noonan believed they had reached Howland's charted position, which was incorrect by about five nautical miles (10 km). The Itasca used her oil-fired boilers to generate smoke for a period of time but the fliers apparently did not see it. The many scattered clouds in the area around Howland Island have also been cited as a problem: their dark shadows on the ocean surface may have been almost indistinguishable from the island's subdued and very flat profile.

Whether any post-loss radio signals were received from Earhart and Noonan remains unclear. If transmissions were received from the Electra, most if not all were weak and hopelessly garbled. Earhart's voice transmissions to Howland were on 3105 kHz, a frequency restricted in the United States by the FCC to aviation use.[Note 35] This frequency was thought to be not fit for broadcasts over great distances. When Earhart was at cruising altitude and midway between Lae and Howland (over 1,000 miles (1,600 km) from each) neither station heard her scheduled transmission at 0815 GCT.[165] Moreover, the 50-watt transmitter used by Earhart was attached to a less-than-optimum-length V-type antenna.[166][167][Note 36]

The last voice transmission received on Howland Island from Earhart indicated she and Noonan were flying along a line of position (running N–S on 157–337 degrees) which Noonan would have calculated and drawn on a chart as passing through Howland.[168][Note 37] After all contact was lost with Howland Island, attempts were made to reach the flyers with both voice and Morse code transmissions. Operators across the Pacific and the United States may have heard signals from the downed Electra but these were unintelligible or weak.[169][Note 38]

Some of these reports of transmissions were later determined to be hoaxes but others were deemed authentic. Bearings taken by Pan American Airways stations suggested signals originating from several locations, including Gardner Island (Nikumaroro), 360 miles (580 km) to the SSE.[170][171] It was noted at the time that if these signals were from Earhart and Noonan, they must have been on land with the aircraft since water would have otherwise shorted out the Electra's electrical system.[172][Note 39][173][Note 40] Sporadic signals were reported for four or five days after the disappearance but none yielded any understandable information.[174][Note 41] The captain of USS Colorado later said: "There was no doubt many stations were calling the Earhart plane on the plane's frequency, some by voice and others by signals. All of these added to the confusion and doubtfulness of the authenticity of the reports."[175]"