Avioncito literally means "little airplane," as it's the diminutive form of avión (airplane).
However, in this song, it's used as slang associated with drinking tequila. The phrase "hacer el avioncito" refers to the ritual of taking a shot: salt, tequila, then lime. Snow Tha Product pairs tequilita y avioncito to paint a vivid picture of drinking to cope with a breakup, making this a clever and culturally specific word choice.
Ever bought your partner a house, a car, and even a dog, only to have them walk out on you anyway? That is exactly the kind of mess Snow Tha Product is dealing with here. She lays it all out with dark humor: "Compré casa, compré carro, compré perro / Y al final el pinche perro me dejó" ("I bought a house, I bought a car, I bought a dog / And in the end the damn dog left me"). She hustled to provide for both of them, but her ex complained about family gossip, her lifestyle, and not being the center of attention. Now the ex keeps blowing up her phone, which leads to the sarcastic hook: "¿Qué tanto me llamas si soy lo peor?" ("Why are you calling me so much if I'm the worst?").
Instead of staying bitter, she takes off. She orders "tequilita y avioncito" ("a little tequila and an airplane [shot]"), walks away to see if life treats her better, and hires a brass band. She starts shouting out regional Mexican music legends to nurse the hangover, calling for old-school hits from Chalino Sánchez, Vicente "Chente" Fernández, Pedro Infante, and Jenni Rivera. When she demands "toquen Banda Jerez por esa cabrona" ("play Banda Jerez for that bitch"), she is asking for the notoriously rowdy, party-heavy brass music from Zacatecas to drown out her ruined wedding plans. It is loud, petty, funny, and deeply satisfying.