Cook the 8 ounces lo mein noodles according to package directions. Drain and set aside.
Add 2 cups broccoli florets and water to a large saucepan. Simmer for 3–5 minutes until tender. Drain and set aside.
Slice the 8 ounces flank steak into thin strips against the grain. Toss with 1 tablespoon sesame oil, 1 teaspoon salt, ½ teaspoon black pepper, 3 teaspoons minced garlic, and minced 1 teaspoon ginger.
Place the seasoned steak in the air fryer and cook at air fryer temperature of 400 degrees F for 3 minutes. Add the diced 1 red bell pepper, 8 ounces sliced water chestnuts, and 1 medium carrot. Cook an additional 3–5 minutes, until the vegetables are tender and the beef is fully cooked.
In a small bowl, whisk together ¼ cup brown sugar, ½ cup soy sauce, 2 tablespoons hoisin sauce, 1 teaspoon sriracha, and 2 teaspoons sesame oil.
Combine the cooked beef and vegetables with the prepared noodles and broccoli. Pour the sauce over the mixture and toss until evenly coated.
Sprinkle with sesame seeds and diced green onions before serving. Serve warm.