Season 21 aired between 18 Sep 2017 and 22 Dec 2017, 18 episodes.
Episodes
E01
Springtime for Diesel
18 Sep 2017
E02
A Most Singular Engine
19 Sep 2017
E03
Dowager Hatt's Busy Day
20 Sep 2017
E04
Stuck in Gear
21 Sep 2017
E05
Runaway Engine
22 Sep 2017
E06
P.A. Problems
25 Sep 2017
E07
Hasty Hannah
26 Sep 2017
E08
Cranky at the End of the Line
27 Sep 2017
E09
New Crane on the Dock
28 Sep 2017
E10
Unscheduled Stops
29 Sep 2017
E11
Phillip's Number
02 Oct 2017
E12
The Fastest Red Engine on Sodor
03 Oct 2017
E13
A Shed for Edward
04 Oct 2017
E14
The Big Freeze
01 Dec 2017
E15
Emily in the Middle
06 Dec 2017
E16
Terence Breaks the Ice
11 Dec 2017
E17
Daisy's Perfect Christmas
18 Dec 2017
E18
Confused Coaches
22 Dec 2017