These stickers feature a unique representation of a Baltimore City character!
The Baltimore Police Department's aviation unit's Eurocopter EC 120 helicopters are frequently referred to as "Foxtrot" due to the tail marking. This name lends itself to the phonetic alphabet variation of WTF: Whiskey Tango Foxtrot. As in, "WTF is happening that's causing Foxtrot to shine a spotlight on my house?" or "WTF are the BPD up to in the sky right now?"
From a 2012 article:
Baltimore Police Unveil New Helicopters
By Adam Bednar, Patch Staff
Baltimore City police flight officers Matthew Hart and Cory Gronchowski said the hardest part of flying over a city is finding an emergency landing spot that won't put anyone on the ground in jeopardy if there's a problem.
"Where can I go in case of an emergency?" Hart asked rhetorically.
But with the arrival of a new fleet of four new Eurocopter EC 120 helicopters, aka "Foxtrot," they have a little more peace of mind that something won't go wrong while flying over Baltimore.
Police spokesman Anthony Guglielmi said the helicopters have been valuable assets, doing everything from pursuing dirt bikes to finding marijuana grows in the city.