What is one key restriction in trip trades according to the established rules?

In the context of trip trades within established rules, the core restriction is that RAPs (Reserve Availability Periods) cannot be traded for trips. This limitation is crucial for maintaining the integrity and scheduling efficiency of crew assignments. By restricting the trading of RAPs, the system ensures that reserve pilots are available to cover unexpected scheduling needs without being compromised by trading their availability for other trips. This policy helps improve operational reliability and ensures that all pilots and crew members adhere to fair trading practices without jeopardizing the overall schedule management.

The other options may imply trading flexibilities or conditions that either do not align with established practices or might misrepresent the nature and governance rules surrounding trip trades in aviation, emphasizing the importance of clarity in trade practices among pilots.