.. the unique U.S system of ‘implied’ crossing clearance enroute to departure runway has always bemused me. I guess the main driver has been unloading the SMC frequency (seems brave given the possible implications) .. another one that gets me all goosed up and tingly is the practice of ‘clear to land’ when in a sequence queue (in the same league as conditional line-up clearances IMHO) … I mean if ****e turns to trumps (freq fail, runway occupied by preceding departure abort or landing debacle) and the subsequent aircraft has already been cleared to land .. well .. who knows what might result? … empirical data and experience might suggest the problem does not exist .. YET … in any event, it seems counter intuitive to me! … that said, the question remains, one of risk management and resources I guess!
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.. there is no doubt we all learn from tragedies like LEX … I will say though, (irrespective of the conversation on the flight deck) … IMHO, this crew were led into this accident sequence by a number of other unrelated factors i.e.
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- outside visual reference confusing (similarity of expectation), without sufficient error triggers (markings, signs etc)
- normalised deviation (expected lighting outages)
- pre-departure flight deck workload, including CRM difficulties from ground steering necessitating the captain taxiing to line-up (FO head down until on centreline, Captain head-out the front during the whole exercise …which is just asking for an instrument cross check error IMHO)
- Lack of automated aural error queues to the crew on the flight deck (avionics) and the ATC (SMD + position alarms)
.. in this day and age, there is no excuse for the presence of any of these holes in the cheese !
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… the old maxim comes to mind ..
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' …. you think safety is expensive ... try having an accident!' 
