Cassini's final flyby of Titan in April 2017 sealed it's fate in September of that year. This is described further in answers to [What force is bringing Cassini down into Saturn's atmosphere in another 145 days; drag, or…?](https://space.stackexchange.com/q/21261/12102)

**Question:** If Cassini's final flyby of Saturn's moon Titan is the 127th Titan flyby, why is it called "T-126"?

 - [Titan Flyby **T-126**: Final Close Encounter, Gateway to the Grand Finale](https://solarsystem.nasa.gov/news/13019/titan-flyby-t-126-final-close-encounter-gateway-to-the-grand-finale/)

>So Long, and Thanks for All the <s>Fish</s> Science  (slightly edited for "clarity")

>Cassini’s **127th** and final close flyby of Titan marks the end of Cassini’s Ring-Grazing Orbits and sets the stage for the mission’s Grand Finale.

 - [Cassini Completes Final -- and Fateful -- Titan Flyby](https://www.nasa.gov/feature/jpl/cassini-completes-final-and-fateful-titan-flyby)

>The spacecraft made its **127th** and final close approach to Titan on April 21 at 11:08 p.m. PDT (2:08 a.m. EDT on April 22), passing at an altitude of about 608 miles (979 kilometers) above the moon's surface.

From the first link:

    Date: April 22, 2017
    Altitude: 608 miles (979 km)
    Speed (relative to Titan): 13,000 mph (5.8 km/sec)