[4]: 37:00 [6] As The Phantom Empire's brief pre-production overlapped with the filming of Commando Squad, the director started making arrangement with players from that movie, such as the two leads Ross Hagen and Dawn Wildsmith, who was also Ray's wife.

But two days later, upon watching the dailies with cinematographer Gary Graver, the latter encouraged Ray to complete the movie right away, as the material looked superior to Commando Squad and he was soon due to depart for other commitments.

[5]: 2:35 [4]: 38:56  Ray was apprehensive about shooting on such a short schedule, so he scoured his B-movie collection to try and find ways to keep the film interesting while relying on time-saving master shots.

[4]: 24:30  To add depth to her mute character, Michelle Bauer incorporated body language derived from that of New Guinea tribespeople she had seen in a National Geographic documentary.

[5]: 22:28  On the other hand, Sybil Danning, who was cultivating a tough and stoic image at the time, asked Ray to cut one of her monologues and replace it with a simple nod.

The supplemental material, which brought back most of the main cast, was shot in Summer 1988 [per a DVD extra, although this is uncertain as the film's copyright is 1987] over a single day at Vasquez Rocks near Los Angeles.

[4]: 1:19:14 The Phantom Empire was the first project fully directed by Ray for his fledgling American Independent Productions (although the patchwork films Death Farm and Evil Spawn were the company's first releases), but remained in limbo for about two years.

assessed that the film was "an affectionate nod to old-time lost world sci-fi pics, which should amuse home video fans" and "ingeniously ma[de] up for lack of resources by stressing snappy dialog and in-jokes".

[23] In the magazine Space Monsters, a movie-centric spinoff of UFO Universe, Dave Jenkins wrote that "[d]espite the low budget of the film, it moves at a nice pace and for the most part the comedy works."

[24] In his syndicated column, Steve Hurst of British publication Video Week called it "another wonderful mish-mash of awfulness from [Ray]" and "[g]reat fun" despite a "rather confused storyline".

[25] Another British syndicated columnist, John Brooker, called it "a must for any tacky film festival" with "[w]ooden acting, rickety sets, juvenile script—in fact everything a B-movie fanatic could ask for".

[20] John Charles of Video Watchdog assessed that "[f]or all of its abundant flaws, The Phantom Empire still manages to be reasonably enjoyable, primarily for its gleeful incorporation of so many genre clichés and the fun the cast has with the material.

"[27] Mike Mayo, author of VideoHound's Horror Show wrote that the film made Fred Olen Ray's claim of a six-day shoot "easy to believe", while calling the monsters "silly" and the humor "frivolous".

[29] In The Dinosaur Filmography, film history Mark F. Berry was unenthusiastic, noting that "[o]n the flip side, Phantom Empire does offer some sharp dialogue delivered by marginally interesting characters", but the "midsection is heavily padded with yawn inducing filler.