The company says it failed to record a $4.6 million aircraft lease expense.
The carrier's stock price dropped nearly 16 percent by the end of trading wednesday. Including the additional expense, Midwest had net income of $3.6 million. Last week, the company had reported net income of $6.6 million.
Midwest senior vice president Carol Skornicka says the firm failed to follow accounting standards that took effect January first in reporting the lease expense. The firm had planned to record the expense in future quarters.
She attributes the revision to human error.