Under JAR-OPS 1 :
Unless ETOPS approved an operator shall not operate a 2 eng A/C over a route which contains a point further from an adequate aerodrome than 60 minutes in case of a Perf Class A A/C with 20 or more seats or a MTOW of 45360 kgs or more .
The 60 minutes range determined at the one engine inop cruise true airspeed, not execeeding VMO under the following :
1-ISA conditions
2-Level flight for turbojet A/C at FL170 or at the max level which the A/C with one eng inop can climb, and maintain, using the gross rate of climb specified in the AFM, whichever is less .
3-Max cont. thrust on the remaining eng.
4-at an A/C weight not less than that resulting from take off at sea level at max take off weight + all eng climb to opt LRC altitude + all eng cruise at LRC speed until time elaped since take off is equal to the threshold of 60 minutes .
The resulting one eng inop cruise speed and max distance from an adequate airport should be included in the operation manual .
I think for smaller Perf.A A/C's limitation goes to 120 minutes and again I think for Perf.B & C limit is 120 minutes or 300NM whichever is less .