Rumours of the high-profile visit had been a topic of international interest due to current US-China tensions. The Speaker's office never confirmed the visit but several news organisations reported it before she landed.
Flightradar24 claimed this resulted in "unprecedented, sustained interest" as people used the website to track the flight.
The surge in demand almost crashed the website, it reported in a blog post.
"Our teams immediately began efforts to maintain the stability of our services. Unfortunately, due to the volume of users, it was necessary to deploy our waiting room functionality, which meters access to Flightradar24 for non-subscribers."
Pelosi's visit makes her the third-highest ranking official in the US government and highest ranking US official to visit Taiwan since 1997.
She did visit Taiwan in 1999 but was not in a leadership position at the time.
Officials at the Pentagon had warned Pelosi against travelling to Taiwan as it could prompt retaliation from China.
Former Prime Minister John Key described her visit to Taiwan as "reckless" and "dangerous".
"It was provocative, and it was actually dangerous," he told TVNZ's Q+A with Jack Tame.
On Tuesday, Flightradar24 tracked almost 220,000 flights, according to its website.
The service began as a hobby project between two Swedish aviation enthusiasts and provides real-time information about aircraft.
