NATIONAL NEWS (CNN) — Endeavour will do flyovers Friday of Los Angeles, Sacramento and San Francisco atop a modified jumbo jet -- weather permitting -- then land back at Los Angeles International Airport to end its three-day journey to its retirement home.
Good visibility is key, since the purpose of the flight up the state of California and back is to show off Endeavour to the American public from the sky, and NASA encourages onlookers to share their sightings of the airborne spectacle on social media.
NASA delayed Friday's take off by an hour to 8:15 a.m. PDT "to increase the probability that fog over the San Francisco area will dissipate before the flyover," according to the space agency's website.
After its day trip is done, the orbiter will be removed from its perch atop the Boeing 747 that has carried it cross-country from Florida's Kennedy Space Center. It's final destination is L.A.'s California Science Center, where it will go on display for posterity.
NASA said the shuttle will be moved over roads on October 12-13 to its final spot at the science museum.
On Thursday, it flew low over Tuscon, Arizona, where Mark Kelly, who was the commander on the last Endeavour mission, watched with his wife, former congresswoman Gabby Giffords, before touching down at Edwards Air Force Base in California.
Kelly, who was in space when Giffords was shot and six others were killed in January 2011, said it was emotional to see the orbiter again.
"The space shuttle is really a testament to American engineering and ingenuity," he told CNN affiliate KOLD. "It is the most amazing spacecraft ever built, by far."
His wife had watched the launch of his mission but missed the landing, so it was great for her to see the shuttle in the air, he added.
Endeavour, along with Discovery, Enterprise and Atlantis, became a museum piece after NASA ended its 30-year shuttle program in July 2011.
Two other shuttles -- Challenger and Columbia -- were destroyed in accidents that killed all aboard. Challenger exploded shortly after launch in 1986, and Columbia broke apart upon re-entry into Earth's atmosphere in 2003.
Endeavour's three-day piggyback flight was divided into three legs that could be described as scenic routes to showcase the shuttle to the public from coast to coast.
Social media users have shared Endeavour sightings via the hashtags #spottheshuttle and #OV105, the later being Endeavour's "vehicle designation."
Wednesday's leg took Endeavour to Houston, with flyovers along Florida's Space Coast, Stennis Space Center in Mississippi and the Michoud Assembly Facility in New Orleans.
As Endeavour bid farewell to Kennedy Space Center, it elicited strong emotions from people -- such as CNN iReporter Randy Lathrop of Cocoa, Florida -- who have lived with the shuttle program nearby for decades.
"It's the last time that she'll ever be at her home base again. It strikes a chord of nostalgia in you because she's done so many flights from the space center. This is her home," Lathrop said.
Named for the first ship commanded by British explorer James Cook, Endeavour rolled off the assembly plant in Palmdale, California, in 1991 at a cost of $1.7 billion. It was the baby of the shuttle fleet, built as a replacement for Challenger.
Over the next 20 years, Endeavour flew some of the most high-profile shuttle missions, covering 25 flights and nearly 123 million miles. It flew a Spacelab mission and numerous International Space Station assembly missions and rendezvoused with Russia's Mir Space Station.