Pilots don't want to be promoted to captains anymore, and it's becoming a huge problem for airlines.Thierry Monasse/Getty Images Pilots are avoiding captain promotions due to unpredictable schedules, Reuters reported. United failed to fill 50%, or 978 captain vacancies in the past year, it reported. Captain shortages could cause significant flight disruptions. Pilots are turning down promotions to become captains and this could end up being a huge headache for airlines that are only just emerging from a COVID-19 pandemic slump.Despite the lure of a bigger paycheck, multiple United Airlines pilots, analysts, and union officials told Reuters in a report published July 19 that pilots were shunning captaincies due to unpredictable flying schedules.Phil Anderson, a first officer with United, told the outlet that if he took up the promotion, he "would've ended up divorced and seeing my kids every other weekend."United failed to fill 978 captain vacancies in the past year or around 50% of all vacancies posted by the airline, Reuters reported, citing data from the United pilot union.