The Gresley class P2 was popular in the 1930s
Volunteers who built the first steam engine to run on the UK mainline for almost 50 years, are planning to build a second locomotive.
Tornado was unveiled in 2008 after being funded and assembled by steam enthusiasts in Darlington, Co Durham, in an 18-year project costing £3m.
The A1 Steam Locomotive Trust now wants to build one based on the Gresley class P2 engine - popular in the 1930s.
The trust said a feasibility study would examine what costs were involved.
Trust chairman Mark Allatt said: "It has long been the desire of the trust to build a second locomotive as it would be a great waste to allow the skills and experience that we have developed in the construction of Tornado to go unused.
"However, we first had to ensure the successful commercial introduction of Tornado into main line service and then work to secure her future financially.
Tornado took 18 years of planning, construction and fundraising
He said the debt incurred in the construction of Tornado had been halved and that by the end of June all that will remain to be paid will be a £500,000 bearer bond which is due at the end of 2016.
"In addition, we are able to predict with some confidence our future income streams and set aside funds for maintenance, overhauls and Tornado's support vehicle."
The trust plans to base the new locomotive on the first Gresley class P2 No. 2001 Cock O' the North, which was completed in 1934 by the London & North Eastern Railway (LNER).
However, the P2s never lived up to their potential and they declined with the advent of more streamlined trains in the late 1930s.
The 72ft (22 metre) Tornado is based on the Peppercorn A1 locomotive.