The Senior plc Group traces its history back to the 19th century. The business has changed significantly since that time into an international manufacturing Group that designs, produces and markets high technology components and systems for the principal original equipment manufacturers in the worldwide civil aerospace, defence, diesel engine, exhaust system and energy markets.

Set out below are some of the key events in the Group's history:

1933 Senior Economisers Limited was incorporated when a few employees of Green's Economisers Limited, including Senior's first Chairman, David Lycett Green, set up in opposition.
1947 Senior Economisers Limited became a public company and listed on the London Stock Exchange.
1958 Acquired Senior Hargreaves Limited (formerly called Henry Hargreaves & Sons).
1966 Senior Economisers Limited changed its name to Senior Economisers (Holdings) Limited.
1970 Senior Economisers (Holdings) Ltd was renamed Senior Engineering Group Limited.
1982 Senior Engineering Group Limited re-registered as Senior Engineering Group plc.
1983 Senior acquired Green's Economiser Group plc.
1991 Senior Calorstat SAS (formerly called Calorstat Industries SA) joined the Group.
1992 Senior Automotive Bartlett with its operations near Chicago, Illinois, became part of Senior with the acquisition of Flexonics, Inc and its subsidiary Senior Operations (Canada) Limited (formerly called Flexonics Limited). Senior Automotive Crumlin, South Wales, established.
1994 Acquired Senior Berghofer GmbH (formerly named Christian Berghofer & Co KG) and Senior Aerospace Metal Bellows (formerly the Metal Bellows business of Parker Hannifin Corp.).
1995 Acquisition of the Stainless Steel Products business (now known as Senior Aerospace SSP, based at Burbank, California) and Ermeto-Hydexco SA in France (now known as Senior Automotive Blois and Senior Aerospace Ermeto).
1997 Sold the original economiser business upon the commencement of the Industrial disposal programme. Acquired the business of Senior Aerospace Ketema, based in San Diego, California. A South African automotive business is established in Cape Town.
1998 Acquired Senior Aerospace Bosman B.V. (formerly called Bosman Powersource Support BV). Gained control of Senior India Private Limited (formerly called Inalsa Flexonics Limited). Acquisition of share capital of Senior Aerospace Jet Products (formerly called Jet Products Corporation). Brazilian automotive business is established.
1999 The holding company changed its name from Senior Engineering Group plc to Senior plc. Acquired the entire issued share capital of Senior Flexonics Pathway (formerly called Pathway Bellows Inc.). Acquired Senior Aerospace BWT, Senior Aerospace Bird Bellows, and Senior Aerospace Composites, as part of the purchase of the Aerospace Ducting Division of Cork Industries Limited.
2000 A new automotive factory at Olomouc, Czech Republic is built. Strategy implemented to focus the Group primarily on the Aerospace and Automotive sectors. Commenced the disposal of various industrial businesses.
2004 Completed the Industrial disposal programme which concluded the re-focusing of the Group as an international manufacturing Group supplying to the original equipment producers in the worldwide aerospace and automotive markets.
2006 Acquired Sterling Machine Co., Inc. and Aerospace Manufacturing Technologies, Inc.
2007 Acquired Absolute Manufacturing, Inc.
2008 Acquired Capo Industries, Inc.
2010 Acquired WahlcoMetroflex, Inc.
2011 Acquired Damar Machine Company, Weston EU and Weston SEA
2012 Sold Senior Hargreaves Limited to M+W Group. Acquired GAMFG Precision, LLC.
2013 Acquired Atlas Composites Limited and Thermal Engineering Limited.
2014 Acquired UPECA Technologies Sdn. Bhd.
2015 Acquired Lymington Precision Engineering (LPE) Limited and Steico Industries Inc.