What is a primary concern when boarding passengers while engines are running?

When boarding passengers while engines are running, jet blast safety is a primary concern because the powerful airflow created by the engines can pose a significant danger. Jet blast can create strong winds that may affect the stability of passengers moving toward the aircraft or those boarding. It could potentially blow objects or even cause injuries to individuals who are not properly positioned. Ensuring that passengers are aware of this hazard and that safety measures are in place to mitigate its risks is crucial for a safe boarding process.

While crew readiness, fuel efficiency, and weather conditions are important considerations, they do not pose the immediate physical threat that jet blast safety does during the boarding process.