Ferrocarril del Istmo de Tehuantepec

Rail lines in the Isthmus of Tehuantepec region began constructing in the late 19th century, with the first being the Puerto Mexico (Coatzacoalcos)-Salina Cruz line in 1907, for interoceanic freight service. Rail development continued into the late 20th century, driven by oil exploration and refinement projects in the region.

The Mexican Secretariat of Finance and Public Credit founded the Ferrocarril del Istmo de Tehuantepec (FIT) on March 3, 1999, in order to operate the rail line between Salina Cruz, Oaxaca and Medias Aguas, Veracruz, as well as the construction and operation of a rail line between Medias Aguas and Coatzacoalcos.

Ferrocarriles Chiapas-Mayab (FCCM), a subsidiary of Genesee & Wyoming (G&W), operated other rail lines in the region from 1999 to 2007 under a 30-year concession with the Mexican government; however, due to damages caused Hurricane Stan in 2005, G&W determined that it was economically infeasible to repair the rail lines and relinquished its concession to the Secretariat of Communications and Transportation in 2007, as well as liquidating FCCM. The rail lines and remaining assets were later transferred to FIT.

Redevelopment

On 7 June 2020, President Andrés Manuel López Obrador authorized the renovation of railway tracks and rehabilitation as passenger transport; the work was given an initial investment of more than 3 billion pesos, with about 20 billion pesos total planned to be allocated for this project.

On 17 September 2023, President Andrés Manuel López Obrador inaugurated Line Z for freight transport. On 22 December, passenger service began on Line Z. Later, on 13 September 2024, passenger service on Line FA opened.

A derailment of Line Z near Asunción Ixtaltepec, Oaxaca, on 28 December 2025 left 13 people dead and around 100 more injured.

In August 2023, the website Railtech.com reported a number of InterCity 125 high-speed train sets, originally built for British Rail, had been seen at the Port of Great Yarmouth being loaded on to a ship bound for Mexico. Unconfirmed reports suggested this second-hand rolling stock was bound for the Ferrocarril del Istmo de Tehuantepec.

On 4 September 2023, the news website Diario del Istmo posted a story containing a powerpoint slide from the Sistema Portuario Nacional, confirming that a group of three Class 43 locomotives and 11 Mark 3 coaches had been exported to Mexico for use on Ferrocarril del Istmo de Tehuantepec. In Great Britain, the Class 43 locomotives were numbered GWR 43022, 43158, and 43170; while the coaches were numbered LNER 41091, 41100, 42026, 42179, 42401, 42402, 42405, 44034, 44061, 44063, 44094.

In addition to these InterCity 125 trainsets, several other types of rolling stock will be used. The Ferrocarril Transístmico purchased three EMD SD70M locomotives from the Union Pacific Railroad, former UP 4378, 4671, and 4674. and 12 passenger cars (including 3 Amfleet cars and the Stampede Pass, a dome car built by the Budd Company in 1954) from the Railway Excursion Management Company (Railexco). The first of the SD70Ms, numbered 4378, were presented on 13 August 2023.Meanwhile, in September 2023, an EMD F59PH locomotive was seen in Mobile, Alabama, reportedly on its way to the Tren Interoceánico. Later, an F59PH, now numbered FIT 3005 would, alongside an SD70M numbered FIT 4671, be used on the inaugural run of Line Z on 22 December that year. FIT 3005 was originally GO Transit 520, and during the late-2010s, this unit (then numbered LTEX 18520) was one of three ex-GO Transit F59PHs leased to Metrolink in the late-2010s. After Metrolink retired the ex-GO units in 2022, 18520 became one of two FIT F59PHs, with the other being the former LTEX 18522 (ex-GOT 522).

Furthermore, five Budd SPV-2000 cars were purchased from Railexco for use on the Tren Interoceánico. According to Railexco's official Facebook account, these cars were once owned by Amtrak, and later, by the Connecticut Department of Transportation.