According to John McCain: A Biography (2009):
His target that day was a solid one—the power plant in Hanoi, the heavily defended capital of North Vietnam
John McCain (2001) has an aerial photograph of the target with the caption:
The view from the air the day John McCain was shot down. His target, a power plant, lies on the right side of the lake, just above the bridge
According to Faith of My Fathers: A Family Memoir (2000) by John McCain:
Today's attack on Hanoi...would be my first attack on the enemy capital. ... Our target was the thermal power plant, located near a small lake almost in the center of the city
The target was a thermal power plant—the target I had attempted to bomb in my last moment of freedom.
According to The Nightingale's Song (1996):
McCain's A-4E Skyhawk was part of a twenty-plane mission getting ready to hit the power plant in Hanoi, another target previously off- limits
Also, while difficult to decipher the OCR text, the 9 April 1973 Kansas City Times seems to say:
On McCain’s last mission, a strike against the Hanoi thermal power plant
Mark McDonald for Knight-Ridder is responsible for writing this about Mai Van On (who claims to have rescued McCain):
With U.S. planes still bombing and strafing their target of the day - a nearby light bulb factory where [Mai Van] On worked as a security guard
in newspapers in Febuary 2000, for example the 6 February 2000 Indianapolis Star , the 6 February 2000 Santa Ana Orange County Register and 5 February 2000 Philidelphia Inquirer.
The Joint Chiefs of Staff (JCS) 94-Target List of North Vietnam bombing targets is published in Aerospace Power Journal (Spring 2001). The Hanoi thermal power plant is target 82. No light bulb factory was a target.
Also, the following are notes of the October 23, 1967, 1:05–3:40 p.m. meeting where the President authorized the strike (McCain being shot down October 26th):
The President: Are we now ready to take the wraps off the bombing?
Secretary McNamara: It depends on what you want to do for the rest of the year. If you open up the ten mile circle the JCS have recommended the power plant and the two bridges.
General Wheeler: I would strongly urge the President not to have a pause. I urge you to open up the ten mile circle and also hit the Phuc Yen airfield.
Secretary Rusk: One serious disadvantage is that every time a new target is added it becomes an act of escalation. I would not rush in with a whole new series of targets.
I have no strong feelings about Phuc Yen but it will have to be hit over and over. It may cost more planes than it will destroy. I do not object to the re-entry into the ten mile circle. But I do believe we should spread these targets out.
Secretary McNamara: There has not been a bunch of these targets.
The President reminded those present that the air field had been authorized previously subject only to winding up the Kissinger talks. Now we have gotten rid of all the excuses. Let's go with it.
Secretary McNamara: If we are going to strike we should hit the two bridges and the power plant. They will be announced as a restrike.
General Wheeler: There is a list of thirteen targets. Some of these are restrikes.
Secretary McNamara: Then we are agreed that Phuc Yen is authorized; the two bridges are authorized, and the power plant is authorized. No more than one of these is to be hit in a single day.
[footnote 5] On October 23 the President lifted the suspension of bombing in the Hanoi prohibited area and ordered attacks on various targets including the Hanoi Thermal Power Plant and the Long Bien and Doumer bridges.
And according to The Joint Chiefs of Staff and The War in Vietnam 1960–1968, part 3:
Admiral Sharp moved immediately to execute the new attacks. ... It took only
three days for ROLLING THUNDER pilots to hit the bridges and the power plant.
However, most of the other targets authorized on 23 October were not struck until November. Some were not bombed at all during 1967.