In a large bowl or glass measuring cup, whisk together the marinade ingredients - orange juice, chipotle sauce, olive oil, cilantro, Worcestershire, yellow mustard, garlic, Tajin and salt. Set aside 1/2 cup of the marinade.
Then pour the remaining marinade over the meat - half over the steak and half over the chicken. I like to marinate the meat in gallon-sized Ziploc bags. Refrigerate the meat and allow it to marinate for 30 minutes or up to two hours.
Air fry the steak at 375 degrees F for 16 - 20 minutes, depending on the thickness of the steak. Flip the steak over halfway through cooking time. Cook to between 140 - 145 degrees F internal temperature for a medium steak.
Air fryer the chicken at 350 degrees F for about 16 minutes, flipping the chicken over halfway through cooking time. Cook until the chicken reaches an internal temperature of at least 165 degrees F.
While the steak and chicken are cooking in the air fryer, heat a large, non-stick skillet over medium heat. Add about a tablespoon of oil to the pan.
Add the sliced peppers and onions. Cook them covered, and stirring occasionally until they are soft and starting to brown. This will take about 10 minutes. Once cooked, pour the reserved 1/2 cup of the marinade over the peppers and onions. Continue to cook for a few minutes until the marinade starts to thicken a bit.
Slice the steak and chicken and stir it into the marinated peppers and onions.
Serve the air fryer fajitas with tortillas, shredded cheddar cheese and sour cream.