Blue Flag (with yellow diagonal stripe), Iracing.com Wiki

In Auto Racing, the Blue flag with the yellow diagonal stripe means that faster cars are approaching. Commonly referred to as the Courtesy Flag, this flag in real life only applies to NASCAR but is used in iRacing for any racing series. The flag is there to tell backmarkers (slower lapped traffic or slower cars in general) to give way to faster cars. Sometimes when the backmarkers fail to adhere to the courtesy flag, they may get a drive-through penalty. In iRacing, the flag behaves a little bit

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Kathiri State of Seiyun in Hadhramaut, Iracing.com Wiki

File:600px Blue HEX-011BC2 Yellow HEX-FFF204 diagonal divided White upper right - lower left.svg - Wikimedia Commons

File:Ukrainian Sea Guard racing stripe.svg - Wikipedia

Duchy of Modena and Reggio, Iracing.com Wiki

IRacing Flags, Iracing.com Wiki

iRacing Tracks Archive

Lithuania, Iracing.com Wiki

iRacing Tracks Archive