I almost always pushback and taxi before I receive the final load data. That is the way my company operates. It has to do with the lead sending the load information to load control, load control's entering the data into the system and the final numbers being datalinked to our flight. Most often it all comes together and we are ready to roll into position on the runway when we arrive.
If that mode of operation is not a direct threat to aviation safety, then I don't know what is.
In most countries, only the Captain is authorized to approve the loadsheet. To do so, he needs to check a number of critical data items that the loadsheet is based upon. A signed copy of the loadsheet is then left along with the Captain's signed acceptance of the maintenance log with ground personnel. This then provides direct evidence of what the aircraft loading and maintenance state of the aircraft was purported to be in the event that the aircraft is completely destroyed in an accident.
To perform a loadsheet check, the Captain needs about 30 to 60 seconds of head-down time to check the sheet itself and sign it. What the heck is happening to the aircraft during this time as it taxys to the hold point? The Captain is necessarily out of the loop.
THEN, data needs to be accurately transferred from the loadsheet for the following:
1. Takeoff data needs to be calculated for the aircraft weight and specific runway and met conditions. This data entry and output must be cross-checked independently by another crew-member.
2. This take-off data then needs to be entered into the engine management system to achieve the correct engine thrust for take-off.
3. This takeoff data will determine the flap setting and this needs to be set on the flap selection.
4. Take-off trim needs to be calculated from the CG position or at least transferred from the loadsheet to the trim wheel setting and cross-checked.
It is not impossible to do take-off data calculations due to a runway change after pushback, but it is obviously is a direct threat to safety of flight.
But your airline ALWAYS does the loadsheet check and the takeoff calculations after pushback and on the run for every takeoff? Please tell me that you are working for an African or other third-world small aircraft airline?
Emirates very nearly had what would have been Australia's worst accident recently in Melbourne when the loadsheet data was either incorrectly entered or the takeoff data was incorrectly calculated and entered by the cockpit crew.
Gentlemen and aviatrixes, this is a no-sh!t heads-up warning to all professional aviators.