CN 2951 to CN 2999 and CN 3800 ot CN 3912 are Tier 4 Credit Units.

The first order (CN 2800-2834) was delivered from Fall 2012 to 2014.

In July 2013, CN cancelled their SD70ace order and replaced it by ordering an additional thirty ES44AC locomotives (2835-2864).

The third batch was delivered late 2014 (2865-2909) and the 10 first units of the 2925-2934 series were delivered as CN 3025-3034, then renumbered a few weeks later.

CN 2951-2975 are Tier IV Credit Units built in 2015 and operate in Canada only.

CN 2976-2983 are Tier IV Credit locomotives delivered in 2016.

CN 2984-2999 and 3800-3805 are Tier IV Credit ES44ACs for delivery commencing in September 2017.

More Tier IV units, 3836-3875, were delivered late 2018 / early 2019 and 3876-3895 were received between May and July 2019.
The latest batch, 3896-3912, is currently on order (late 2019).

3286-3295 are under delivery (January 2023).

2881 and 3011: Wrecked in Walker, LA (June 25, 2020) and returned to service

3009: Wrecked near Portage La Prairie, MB (January 3rd, 2019) and sent OOS to AMP, Dansville, NY

3103: Wrecked in Grande Cache, AB (October 2016), returned to service, then wrecked again in Walker, LA (June 25, 2020) and scrapped on site.