Summary

• The fiery "99" seen in the sky at the end of Back to the Future Part II is simply a side effect of the DeLorean being in the air and spinning after being struck by lightning.
• The lightning strike caused the DeLorean to spin uncontrollably, eventually reaching the necessary 88mph to travel through time.
• While there are theories about the significance of the "99" and its connection to the past and future of the series, the screenwriter Bob Gale explains that it is merely a result of the DeLorean's launch and has no deeper meaning.

A backwards “99” appears in the sky at the end of 1989’s Back to the Future Part II - and while there have been many theories about why this is, there is a single definitive answer. From the moment audiences were introduced to Marty McFly and Dr. Emmett Brown, it was clear that any of the adventures the pair faced would be endlessly engaging. As such, there have been many questions over the years regarding how the DeLorean’s time travel functioned, all of which attest to the franchise’s ongoing appeal.

However, beyond the bigger questions about time travel and the DeLorean, Back to the Future has many blink-and-you-’ll-miss-it moments. One such moment comes just after the DeLorean has been zapped by lightning in the final minutes of Back to the Future Part II. As Marty looks on in horror over his worst nightmare being realized, the disappearance of the DeLorean from the stormy night sky is punctuated by a fiery inverted “99.” This strange occurrence is puzzling as there doesn’t seem to be any reason why “99” should appear – or even if what’s seen in the sky is, in fact, a “99.”

Back To The Future 2's Spinning DeLorean Caused The "99"

They Are Flaming Tire Tracks, Not Numbers

There have been many theories regarding the “99” in the skies of Back to the Future Part II. Some suggest the fiery inverted “99” is a reference to both the past and the future of the series. This is because at the end of Back to the Future Part I, after Marty goes back to 1985, Doc dances in the street. One of the nearby shops is Western Auto, the sign of which is a giant neon nine made out of an arrow. The two nines in Part II are backward – potentially signifying going back in time, and nine plus nine is 18 – a reference to the 1800s.

As interesting as that possibility may be, Back to the Future screenwriter Bob Gale explained in issue 3 of the official Back to the Future Fan Club Magazine that the actual reason for the fiery “99” is simply a side effect of the DeLorean being in the air. As fans know, the DeLorean leaves a trail of fire after reaching 88mph and setting off. However, because the vehicle was in the air at the end of Part II and spinning from having been struck by lightning, it could not shoot off in a straight direction. As a result, the DeLorean’s launch was marked by fire trails that remained stationary.

In 2021, a miniseries was made titled Expedition: Back to the Future, in which Josh Gates and Christopher Lloyd go in search of the original Delorean from the movies. The series is available to stream on Max.

How The DeLorean Time Travels While In The Sky During Back To The Future 2

The Lightning Pushes It Into A High Speed Spin

Another interesting question regarding the fiery inverted “99” is the entire issue of time travel. Everything that fans know about the DeLorean dictates that it must reach 88mph in order to engage in the process of time travel. This can be achieved on the ground or in the air, but it must be done. However, if Doc Brown is sent back to 1889 due to the DeLorean being struck by lightning, a valid question remains how this was possible. There is certainly a considerable amount of power in a bolt of lightning (as Back to the Future Part I taught audiences), but what about reaching 88mph?

Once again, Gale steps up with a suitable answer to satisfy fans. Because a bolt of lightning contains so much power, striking the DeLorean caused the vehicle to spin uncontrollably. This momentum continued until the requisite 88mph was reached, at which point the DeLorean was launched into the past. Gale’s explanation does make sense, but it also creates other questions such as why the DeLorean simply wasn’t obliterated by being struck directly by lighting. Then again, the consistent line of questioning that Back to the Future creates is a big part of its charm, allowing the franchise to still be discussed nearly 40 years after its release.