Upload Files using Ajax and few more variables

I'm trying to sent my mulitple files upload with ajax. Problem is that I need and few more varables (from input field). And I don't know how to send those few more variables (exmp. "city") Hire is my html code:

<input type="text" name="city" class="city">
<input type="file" name="files[]" multiple="multiple" accept="image/*">
<button id="upload">Upload</button>

And javascript

$(document).ready(function (e) {
            $('#upload').on('click', function () {
                var city= $(".city").val();
                var form_data = new FormData();
                var ins = document.getElementById('multiFiles').files.length;
                for (var x = 0; x < ins; x++) {
                    form_data.append("files[]", document.getElementById('multiFiles').files[x]);                        

                    url: 'uploads.php',                       
                    cache: false,                        
                    data: form_data,
                    type: 'post',
                    success: function (response) {
                    error: function (response) {
                        $('#msg').html(response); // display error