Firstly, there was a light bulb factory in Hanoi at this time.
See for example the Asian Recorder volume 9, page 5802 (March 5-11, 1963)
Plant In Hanoi: A light bulb and vacuum flask factory, built with Chinese assistance, was inaugurated in Hanoi on January 8. The factory produces electric bulbs, neon tubes, car light bulbs, torch bulbs, and vacuum flasks. Work on the factory started in 1961 with the help of Chinese experts. At the inauguration ceremony, the Minister of Light Industry, Mr. Kha Vang Can, expressed sincere thanks for the priceless assistance of the Chinese Government and people.
In May of 1967, there were reports that the factory was bombed. See Daily Report: Asia & Pacific:
5, 12 May Raids
Paris AFF in English 1303 GMT 15 May 1967- - E (FOR OFFICIAL USE ONLY)
(Text) 15 May--Jacques Moalic dispatch--A thermos flask and an electric light bulb factory and two buildings North Vietnamese authorities say housed institutes or upper schools were hit by bombs during raids of Hanoi's suburbs on 5 and 12 May
In the Daily Report, Foreign Radio Broadcasts, by the US CIA, is:
VNA International Service in English 1609 GMT 6 May 1967--B (Text: ) Hanoi., 6 May--NHAN DAN in an editorial today highly praised the armed forces and people of Hanoi for downing eight U.S. aircraft and capturing several U.S. air pirates in well-mounted battles yesterday. The paper pointed out that this was one of the quickest, and most bitter defeats of the U.S. aggressors over Hanoi's airspace. By attacking economic establishments and densely populated areas in Hanoi city, the U.S. aggressors have taken an extremely serious step in their war escalation. Like a pack of cornered beasts, they dropped many explosive bombs, and pellet bombs on the Than Long cigarette factory, the soap factory, and the Rung Dong electric bulb and vacuum flask factory. The bloodthirsty Johnson in his capacity as president of the United States himself ordered this barbarous raid against even factories solely intended to serve the people's life.
and Summary of World Broadcasts: Far East, Part 3 (BBC) states:
An editorial in 'Nhan Dan' on 6th May gives high praise to the armed forces and people of Hanoi on inflicting "one of the quickest and most bitter defeats on the US aggressors over Hanoi's air space". The paper states that US aircraft had dropped many high-explosive and pellet bombs on the Than Long cigarette factory, the soap factory and the Rung Dong electric bulb and vacuum flask factory in Hanoi. 'Nhan Dan' adds: "The bloodthirsty Johnson, in his capacity as President of the USA, himself ordered this barbarous raid against factories solely intended to serve the people's life..."
There is also a photograph in Viet Nam Destruction War Damage (1977), "Printed In the Socialist Republic of Viet Nam", with the caption:
Ha Noi electric light-bulb and thermos flask factory (May, 1967)
(the company still exists and still has a factory in Hanoi: Rang Dong Light Source and Vacuum Flask)
However, McCain was shot down on 26 October 1967 and other Americans were shot down and captured in the 5 May attack on Hanoi. Mark McDonald's story (February 2000, Knight-Ridder) of Mai Van On supposedly rescuing McCain on the day the light bulb factory was (allegedly) bombed could be an indication that Mai Van On really rescued a different American.
