diff --git a/src/aircraft_cmd.cpp b/src/aircraft_cmd.cpp
--- a/src/aircraft_cmd.cpp
+++ b/src/aircraft_cmd.cpp
@@ -453,7 +453,7 @@ void Aircraft::OnNewDay()
 
 	if (this->running_ticks == 0) return;
 
-	CommandCost cost(EXPENSES_AIRCRAFT_RUN, this->GetRunningCost() * this->running_ticks / (DAYS_IN_YEAR * Ticks::DAY_TICKS));
+	CommandCost cost(EXPENSES_AIRCRAFT_RUN, this->GetRunningCost() * this->running_ticks / (CalendarTime::DAYS_IN_YEAR * Ticks::DAY_TICKS));
 
 	this->profit_this_year -= cost.GetCost();
 	this->running_ticks = 0;