Thanks....so are you saying if I fly IAS there are built in margins. Any idea where this is written as I have had this discussion with a few people now and you are not the first to say this.....but no one could offer a reference.
For the US, FAA Order 8260.58A, Page 1-13 (for IAS to TAS) and Appendix A for historical winds. The order is on the FAA's website.