[hardwired]

Your code compiles and runs okay. Here's a suggestion.

Code:

import java.awt.*;
import javax.swing.*;

public class FI {
    private JPanel getContent() {
        JLabel title = new JLabel("Flight Info");
        title.setFont(new Font("Serif", Font.BOLD, 30));
        JPanel bannerPanel = new JPanel();
        bannerPanel.setPreferredSize(new Dimension(300, 50));
        bannerPanel.add(title);
        
        JTextField nameInputField = new JTextField();
        JLabel inputAirlineName = new JLabel("Airline Name:     ");
        inputAirlineName.setFont(new Font("Serif", Font.PLAIN, 14));
        JPanel namePanel = new JPanel();
        namePanel.setLayout(new BoxLayout(namePanel, BoxLayout.X_AXIS));
        namePanel.setPreferredSize(new Dimension(200, 20));
        namePanel.add(inputAirlineName);
        namePanel.add(nameInputField);
        
        JLabel inputFlightNum = new JLabel("Flight Number:   ");
        inputFlightNum.setFont(new Font("Serif", Font.PLAIN, 14));
        JTextField flightNumField = new JTextField();          
        JPanel flightNumPanel = new JPanel();
        flightNumPanel.setLayout(new BoxLayout(flightNumPanel, BoxLayout.X_AXIS));
        flightNumPanel.setPreferredSize(new Dimension(200, 20));
        flightNumPanel.add(inputFlightNum);
        flightNumPanel.add(flightNumField);
        
        JLabel inputOrigin = new JLabel("City of Origin:    ");
        inputOrigin.setFont(new Font("Serif", Font.PLAIN, 14));
        JTextField originField = new JTextField();          
        JPanel originPanel = new JPanel();
        originPanel.setLayout(new BoxLayout(originPanel, BoxLayout.X_AXIS));
        originPanel.setPreferredSize(new Dimension(200, 20));
        originPanel.add(inputOrigin);
        originPanel.add(originField);
        
        JLabel inputDestination = new JLabel("Destination City: ");
        inputDestination.setFont(new Font("Serif", Font.PLAIN, 14));
        JTextField destinationField = new JTextField();          
        JPanel destinationPanel = new JPanel();
        destinationPanel.setLayout(new BoxLayout(destinationPanel, BoxLayout.X_AXIS));
        destinationPanel.setPreferredSize(new Dimension(200, 20));
        destinationPanel.add(inputDestination);
        destinationPanel.add(destinationField);

        JPanel blankPanel = new JPanel();
        blankPanel.setLayout(new BoxLayout(blankPanel, BoxLayout.X_AXIS));
        blankPanel.setPreferredSize(new Dimension(200, 20));

        JButton startButton = new JButton("Get Data");
        startButton.setFont(new Font("Serif", Font.PLAIN, 14));
        JButton exitButton = new JButton("Exit");
        exitButton.setFont(new Font("Serif", Font.PLAIN, 14));
        JButton searchButton = new JButton("Search");
        searchButton.setFont(new Font("Serif", Font.PLAIN, 14));
        JButton clearButton = new JButton("Clear");
        clearButton.setFont(new Font("Serif", Font.PLAIN, 14));
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new BoxLayout(buttonPanel, BoxLayout.X_AXIS));
//        buttonPanel.setPreferredSize(new Dimension(250, 20));
        buttonPanel.add(startButton);
        buttonPanel.add(clearButton);
        buttonPanel.add(searchButton);
        buttonPanel.add(exitButton);

        JPanel mainPanel = new JPanel();
        System.out.println("JPanel default layout manager = " +
                            mainPanel.getLayout().getClass().getName());
        mainPanel.add(bannerPanel, BorderLayout.NORTH);
        mainPanel.add(namePanel, BorderLayout.CENTER);
        mainPanel.add(flightNumPanel, BorderLayout.CENTER);
        mainPanel.add(originPanel, BorderLayout.CENTER);
        mainPanel.add(destinationPanel, BorderLayout.CENTER);
        mainPanel.add(blankPanel, BorderLayout.CENTER);
        mainPanel.add(buttonPanel, BorderLayout.SOUTH);
        return mainPanel;
    }

    public static void main(String[] args) {
        // Using the variable "app" will help avoid problems
        // with the static modifier in your class.
        FI app = new FI();
        // creates new instance of JFrame so graph can be displayed
        JFrame f = new JFrame();
        // tells JFrame to close on exit
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(app.getContent());
        f.setSize(300, 265);      // sets size of JFrame
        f.setLocation(200, 200);  // sets location of JFrame
        f.setVisible(true);       // makes JFrame visible
    } // end main
} // end class